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Decompose fractions into unit sums

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5106224
A strip is divided into \(12\) equal parts. Five of those parts make the fraction \(\frac{5}{12}\). a) Write \(\frac{5}{12}\) as a sum of unit fractions. b) Explain how the numerator \(5\) tells you how many unit fractions appear in the sum.

Hints

- What fraction represents one of the \(12\) equal parts? - Think of the numerator as a count of equal unit-fraction pieces. - Check that the number of addends matches the numerator.

Solution

1. One of \(12\) equal parts is the unit fraction \(\frac{1}{12}\). 2. Five equal parts are five copies of \(\frac{1}{12}\): \(\frac{5}{12}=\frac{1}{12}+\frac{1}{12}+\frac{1}{12}+\frac{1}{12}+\frac{1}{12}\). 3. The numerator \(5\) counts the number of \(\frac{1}{12}\) unit fractions in \(\frac{5}{12}\).

Answer

a) \(\frac{1}{12}+\frac{1}{12}+\frac{1}{12}+\frac{1}{12}+\frac{1}{12}\) b) The numerator \(5\) means there are five copies of \(\frac{1}{12}\).
5405994
What fraction in twelfths is represented by the shaded bar? Write the amount first as a sum of unit fractions and then as one fraction.
Figure for problem 540599

Hints

- Determine the unit fraction represented by one part of the bar. - Count the shaded parts rather than using a count supplied in the text. - The number of unit-fraction copies becomes the numerator.

Solution

1. The bar is divided into \(12\) equal parts, so each shaded part represents \(\frac{1}{12}\). 2. There are \(9\) shaded parts, giving \(9\) copies of \(\frac{1}{12}\). 3. Thus the sum is \(\frac{1}{12}+\frac{1}{12}+\frac{1}{12}+\frac{1}{12}+\frac{1}{12}+\frac{1}{12}+\frac{1}{12}+\frac{1}{12}+\frac{1}{12}=\frac{9}{12}\).

Answer

\(\frac{1}{12}+\frac{1}{12}+\frac{1}{12}+\frac{1}{12}+\frac{1}{12}+\frac{1}{12}+\frac{1}{12}+\frac{1}{12}+\frac{1}{12}=\frac{9}{12}\)
5406064
Which unit-fraction sum is greater? Show how you know. \(\frac{1}{6}+\frac{1}{6}+\frac{1}{6}+\frac{1}{6}\) or \(\frac{1}{6}+\frac{1}{6}+\frac{1}{6}+\frac{1}{6}+\frac{1}{6}\)

Hints

- Identify the unit fraction used in both sums. - Count how many copies appear in each sum. - When the unit fractions are the same size, compare the numbers of copies.

Solution

1. The first sum has \(4\) copies of \(\frac{1}{6}\), so it equals \(\frac{4}{6}\). 2. The second sum has \(5\) copies of \(\frac{1}{6}\), so it equals \(\frac{5}{6}\). 3. The unit fractions are the same size, and \(5\) copies are more than \(4\) copies, so the second sum is greater.

Answer

The second sum is greater: \(\frac{5}{6}>\frac{4}{6}\).
5544174
Use the bar to write the shaded amount as a sum of unit fractions. Then write the sum as one fraction.
Figure for problem 554417

Hints

- Count the equal parts in the whole to identify one unit fraction. - Count how many of those equal parts are shaded. - Write one copy of the unit fraction for each shaded part.

Solution

1. The bar is divided into \(5\) equal parts, so one part is \(\frac{1}{5}\). 2. Three parts are shaded, so the unit-fraction sum is \(\frac{1}{5}+\frac{1}{5}+\frac{1}{5}\). 3. Three copies of \(\frac{1}{5}\) make \(\frac{3}{5}\).

Answer

\(\frac{1}{5}+\frac{1}{5}+\frac{1}{5}=\frac{3}{5}\)
5544184
Write \(\frac{4}{5}\) as a sum of unit fractions with denominator \(5\).

Hints

- The denominator tells the size of the unit fraction. - The numerator tells how many copies are needed.

Solution

1. The denominator \(5\) tells us the unit fraction is \(\frac{1}{5}\). 2. The numerator \(4\) tells us to use four copies of that unit fraction. 3. Therefore, \(\frac{4}{5}=\frac{1}{5}+\frac{1}{5}+\frac{1}{5}+\frac{1}{5}\).

Answer

\(\frac{1}{5}+\frac{1}{5}+\frac{1}{5}+\frac{1}{5}\)
5544194
The model shows more than one whole shaded in sixth-sized parts. a) How many copies of \(\frac{1}{6}\) are shaded? b) Write the shaded amount as an improper fraction and as a mixed number.
Figure for problem 554419

Hints

- Identify the size of one equal part in the model. - Count every shaded part across the wholes. - Regroup enough unit fractions to make one whole.

Solution

1. The model shows \(7\) shaded sixth-sized parts. 2. Seven copies of \(\frac{1}{6}\) make \(\frac{7}{6}\). 3. Six sixths make one whole, leaving one sixth, so \(\frac{7}{6}=1\frac{1}{6}\).

Answer

a) \(7\) copies b) \(\frac{7}{6}=1\frac{1}{6}\)
5114194
A unit fraction has a numerator of \(1\), such as \(\frac{1}{2}\), \(\frac{1}{3}\), or \(\frac{1}{10}\). Ancient Egyptians represented fractions as sums of different unit fractions. Write \(\frac{3}{4}\) as the sum of two different unit fractions. Briefly explain your method.

Hints

- Start with a unit fraction that is less than \(\frac{3}{4}\). - Subtract that unit fraction from \(\frac{3}{4}\). - Check whether the remainder is another unit fraction.

Solution

1. Choose a unit fraction less than \(\frac{3}{4}\), such as \(\frac{1}{2}\). 2. Find the difference: \(\frac{3}{4}-\frac{1}{2}=\frac{3}{4}-\frac{2}{4}=\frac{1}{4}\). 3. The remainder is a different unit fraction, so \(\frac{3}{4}=\frac{1}{2}+\frac{1}{4}\).

Answer

\(\frac{3}{4}=\frac{1}{2}+\frac{1}{4}\)
5114224
Consider the fraction \(\frac{3}{10}\). a) Write it as a sum of unit fractions with the same denominator. b) How many unit-fraction addends are in your sum, and what does that number have to do with the numerator of \(\frac{3}{10}\)?

Hints

- A unit fraction has numerator \(1\). - Ask what one of the ten equal parts is called as a fraction. - Relate the number of equal parts being counted to the numerator.

Solution

1. One tenth is the unit fraction \(\frac{1}{10}\). 2. Three tenths are three copies of that unit fraction: \(\frac{3}{10}=\frac{1}{10}+\frac{1}{10}+\frac{1}{10}\). 3. The sum has \(3\) addends. That count matches the numerator \(3\), which tells how many tenths are present.

Answer

a) \(\frac{1}{10}+\frac{1}{10}+\frac{1}{10}\) b) There are \(3\) addends, matching the numerator \(3\).
5114334
A unit fraction can be decomposed into smaller unit fractions. For example, \(\frac{1}{3}=\frac{1}{4}+\frac{1}{12}\). Use this fact to write \(\frac{2}{3}\) in two ways: 1) as a sum of two equal unit fractions; 2) as a sum of three different unit fractions.

Hints

- Use the numerator to write \(\frac{2}{3}\) as repeated thirds. - Replace one third with the equivalent sum given in the problem. - Check that the three denominators in part 2) are different.

Solution

1. Two equal unit fractions give \(\frac{2}{3}=\frac{1}{3}+\frac{1}{3}\). 2. Replace one \(\frac{1}{3}\) with \(\frac{1}{4}+\frac{1}{12}\): \(\frac{2}{3}=\frac{1}{3}+\frac{1}{4}+\frac{1}{12}\).

Answer

1) \(\frac{2}{3}=\frac{1}{3}+\frac{1}{3}\) 2) \(\frac{2}{3}=\frac{1}{3}+\frac{1}{4}+\frac{1}{12}\)
5114344
A unit fraction has a numerator of \(1\), such as \(\frac{1}{2}\), \(\frac{1}{3}\), or \(\frac{1}{10}\). Write \(\frac{5}{6}\) as the sum of two different unit fractions.

Hints

- A unit fraction has a numerator of \(1\). - Find a common denominator before adding fractions with unlike denominators. - Consider unit fractions whose denominators are factors of \(6\).

Solution

1. Look for two unit fractions that can be rewritten with denominator \(6\). 2. Since \(\frac{1}{2}=\frac{3}{6}\) and \(\frac{1}{3}=\frac{2}{6}\), \(\frac{1}{2}+\frac{1}{3}=\frac{3}{6}+\frac{2}{6}=\frac{5}{6}\).

Answer

\(\frac{5}{6}=\frac{1}{2}+\frac{1}{3}\)
5405964
The shaded amount in the bar equals the two written unit twelfths plus a missing unit-fraction sum: \(\frac{1}{12}+\frac{1}{12}+\square\). What sum of unit twelfths belongs in the box?
Figure for problem 540596

Hints

- Read the total shaded amount from the bar. - Compare the number of shaded twelfths with the two unit twelfths already written. - Represent each remaining shaded part with one unit-fraction addend.

Solution

1. Read the bar: \(5\) of its \(12\) equal parts are shaded, so the target amount is \(\frac{5}{12}\). 2. The two written terms account for \(\frac{2}{12}\), leaving \(\frac{3}{12}\). 3. Write that missing amount as \(\frac{1}{12}+\frac{1}{12}+\frac{1}{12}\).

Answer

\(\frac{1}{12}+\frac{1}{12}+\frac{1}{12}\)
5405974
Leo looks at the shaded bar and writes \(\frac{1}{5}+\frac{1}{5}+\frac{1}{5}+\frac{1}{5}+\frac{1}{5}\) for the shaded amount. Explain why Leo's sum is incorrect and write a correct unit-fraction sum for the bar.
Figure for problem 540597

Hints

- First determine what Leo's five identical addends total. - Use the bar to identify the size of one equal shaded part. - The number of shaded parts tells how many copies of that unit fraction are needed.

Solution

1. Five copies of \(\frac{1}{5}\) make \(\frac{5}{5}=1\), so Leo's sum represents a whole. 2. The displayed bar is divided into \(8\) equal parts, with \(5\) shaded. Each shaded part is therefore \(\frac{1}{8}\). 3. The correct sum is \(\frac{1}{8}+\frac{1}{8}+\frac{1}{8}+\frac{1}{8}+\frac{1}{8}=\frac{5}{8}\).

Answer

Leo's sum equals \(1\), not the shaded amount. A correct sum is \(\frac{1}{8}+\frac{1}{8}+\frac{1}{8}+\frac{1}{8}+\frac{1}{8}\).
5405984
Use the model shown. a) Write the shaded amount as a sum made only of unit fractions. b) How many terms are in the sum?
Figure for problem 540598

Hints

- Identify the unit fraction represented by one equal part of a bar. - Count the shaded equal parts across both wholes. - Use one unit-fraction addend for each shaded part.

Solution

1. Each whole is divided into thirds, so each shaded part represents \(\frac{1}{3}\). 2. The model shows \(5\) shaded thirds in all, representing \(1\frac{2}{3}=\frac{5}{3}\). 3. Therefore, the unit-fraction sum is \(\frac{1}{3}+\frac{1}{3}+\frac{1}{3}+\frac{1}{3}+\frac{1}{3}\), which has \(5\) terms.

Answer

a) \(\frac{1}{3}+\frac{1}{3}+\frac{1}{3}+\frac{1}{3}+\frac{1}{3}\) b) \(5\) terms
5406004
Two shaded parts are removed from the bar shown. a) Write the remaining amount as a unit-fraction sum. b) Write the remaining amount as one fraction.
Figure for problem 540600

Hints

- Read the starting number of shaded tenths from the bar. - Remove the stated number of shaded parts. - Use one \(\frac{1}{10}\) addend for each part that remains.

Solution

1. The bar is divided into tenths and begins with \(9\) shaded parts. Removing \(2\) leaves \(7\) shaded tenths. 2. The remaining unit-fraction sum is \(\frac{1}{10}+\frac{1}{10}+\frac{1}{10}+\frac{1}{10}+\frac{1}{10}+\frac{1}{10}+\frac{1}{10}\). 3. Seven copies of \(\frac{1}{10}\) equal \(\frac{7}{10}\).

Answer

a) \(\frac{1}{10}+\frac{1}{10}+\frac{1}{10}+\frac{1}{10}+\frac{1}{10}+\frac{1}{10}+\frac{1}{10}\) b) \(\frac{7}{10}\)
5406024
The fraction \(\frac{5}{6}\) is five copies of \(\frac{1}{6}\). Two copies are removed. a) Write the remaining amount as a unit-fraction sum and as one fraction. b) Write the removed amount as one fraction. c) Write an equation showing that the remaining amount plus the removed amount equals \(\frac{5}{6}\).

Hints

- Think of the numerator \(5\) as a count of five unit sixths. - Keep track separately of the copies that remain and the copies that were removed. - For the final equation, use sixths so the two groups visibly rebuild the original five copies.

Solution

1. Removing two of the five unit sixths leaves three copies: \(\frac{1}{6}+\frac{1}{6}+\frac{1}{6}=\frac{3}{6}=\frac{1}{2}\). 2. The two removed copies total \(\frac{2}{6}=\frac{1}{3}\). 3. Using denominator \(6\), the parts recombine as \(\frac{3}{6}+\frac{2}{6}=\frac{5}{6}\).

Answer

a) \(\frac{1}{6}+\frac{1}{6}+\frac{1}{6}=\frac{3}{6}=\frac{1}{2}\) b) \(\frac{2}{6}=\frac{1}{3}\) c) \(\frac{3}{6}+\frac{2}{6}=\frac{5}{6}\)
5406034
Nora writes \(\frac{1}{2}=\frac{1}{6}+\frac{2}{6}\) and says the right side is a unit-fraction sum. a) Explain why her description is incorrect. b) Rewrite only \(\frac{2}{6}\) as unit fractions so the equation becomes a valid unit-fraction sum.

Hints

- Check the numerator of each addend against the definition of a unit fraction. - Ask how many copies of \(\frac{1}{6}\) make \(\frac{2}{6}\). - Verify that the rewritten right side still equals one half.

Solution

1. A unit fraction has numerator \(1\), so \(\frac{2}{6}\) is not a unit fraction. 2. The fraction \(\frac{2}{6}\) is two copies of \(\frac{1}{6}\). 3. Therefore, \(\frac{1}{2}=\frac{1}{6}+\frac{1}{6}+\frac{1}{6}\), which is a valid unit-fraction sum because \(\frac{3}{6}=\frac{1}{2}\).

Answer

a) \(\frac{2}{6}\) is not a unit fraction because its numerator is not \(1\). b) \(\frac{1}{2}=\frac{1}{6}+\frac{1}{6}+\frac{1}{6}\)
5406044
The two models show the same amount. a) Write the amount as a sum of unit halves. b) Write the amount as a sum of unit fourths. c) Which representation uses more terms, and how many more?
Figure for problem 540604

Hints

- Count the shaded equal parts in model a) and identify the unit fraction for one part. - Do the same for model b). - Compare the two numbers of unit-fraction addends.

Solution

1. Model a) shows \(3\) shaded halves, so the amount is \(\frac{3}{2}=1\frac{1}{2}\) and the unit-half sum is \(\frac{1}{2}+\frac{1}{2}+\frac{1}{2}\). 2. Model b) shows the same amount as \(6\) shaded fourths, so the unit-fourth sum is \(\frac{1}{4}+\frac{1}{4}+\frac{1}{4}+\frac{1}{4}+\frac{1}{4}+\frac{1}{4}\). 3. The fourths representation uses \(6-3=3\) more terms.

Answer

a) \(\frac{1}{2}+\frac{1}{2}+\frac{1}{2}\) b) \(\frac{1}{4}+\frac{1}{4}+\frac{1}{4}+\frac{1}{4}+\frac{1}{4}+\frac{1}{4}\) c) The fourths representation uses \(3\) more terms.
5406054
Riley says the shaded bar is represented by eight copies of \(\frac{1}{12}\). Is Riley correct? If not, add or remove the fewest possible copies of \(\frac{1}{12}\) to make the unit-fraction sum match the bar.
Figure for problem 540605

Hints

- Read the shaded fraction from the bar first. - Rename that fraction in twelfths to find how many unit twelfths it contains. - Compare that count with Riley's eight copies.

Solution

1. The bar shows \(\frac{3}{4}\) shaded. 2. In twelfths, \(\frac{3}{4}=\frac{9}{12}\), so the bar represents nine copies of \(\frac{1}{12}\). 3. Riley used eight copies, so one more \(\frac{1}{12}\) is needed.

Answer

Riley is not correct. Add one copy of \(\frac{1}{12}\); the correct sum has nine copies of \(\frac{1}{12}\).
5406074
Maya looks at the model and says the shaded amount is \(1\frac{1}{3}\). Is Maya correct? Show how the unit fractions can be regrouped into a whole and a remaining fraction.
Figure for problem 540607

Hints

- Use the model to identify the unit fraction and count its shaded copies. - Regroup enough copies to make one whole. - Simplify the fraction represented by the copies left over.

Solution

1. Each shaded part is \(\frac{1}{6}\), and the model contains \(8\) shaded parts, so the total is \(\frac{8}{6}\). 2. Six sixths make one whole, leaving \(\frac{2}{6}\). 3. Since \(\frac{2}{6}=\frac{1}{3}\), the total is \(1\frac{1}{3}\). Maya is correct.

Answer

Yes. \(\frac{8}{6}=1\frac{2}{6}=1\frac{1}{3}\).
5406084
Twelve copies of \(\frac{1}{12}\) are divided into three equal groups. a) Write the unit-fraction sum in each group. b) What fraction does each group equal?

Hints

- Divide the number of identical terms equally among the three groups. - For part a), write one unit fraction for each term in a group. - For part b), combine and simplify the four twelfths.

Solution

1. Divide the twelve terms equally among three groups: \(12\div3=4\) terms per group. 2. Each group is \(\frac{1}{12}+\frac{1}{12}+\frac{1}{12}+\frac{1}{12}=\frac{4}{12}\). 3. Since \(\frac{4}{12}=\frac{1}{3}\), each group equals \(\frac{1}{3}\).

Answer

a) \(\frac{1}{12}+\frac{1}{12}+\frac{1}{12}+\frac{1}{12}\) b) \(\frac{1}{3}\)
5407244
Each small section in the bar represents \(\frac{1}{12}\) of the whole. The colors separate the shaded unit twelfths into three groups. a) How many copies of \(\frac{1}{12}\) are blue, orange, and green? b) Write the entire shaded amount as a unit-fraction sum and as one fraction. c) Write the unshaded amount as a unit-fraction sum and as one fraction.
Figure for problem 540724

Hints

- Count the small sections in each color group; every small section has the same value. - For the shaded total, combine the counts before writing the numerator. - For the unshaded amount, count the white sections and use the same unit fraction.

Solution

1. The blue group has \(3\) unit twelfths, the orange group has \(2\), and the green group has \(4\). 2. Altogether there are \(3+2+4=9\) shaded unit twelfths. The expanded sum is \(\frac{1}{12}+\frac{1}{12}+\frac{1}{12}+\frac{1}{12}+\frac{1}{12}+\frac{1}{12}+\frac{1}{12}+\frac{1}{12}+\frac{1}{12}=\frac{9}{12}=\frac{3}{4}\). 3. Three sections are unshaded, so the unshaded amount is \(\frac{1}{12}+\frac{1}{12}+\frac{1}{12}=\frac{3}{12}=\frac{1}{4}\).

Answer

a) Blue: \(3\); orange: \(2\); green: \(4\) b) \(\frac{1}{12}+\frac{1}{12}+\frac{1}{12}+\frac{1}{12}+\frac{1}{12}+\frac{1}{12}+\frac{1}{12}+\frac{1}{12}+\frac{1}{12}=\frac{9}{12}=\frac{3}{4}\) c) \(\frac{1}{12}+\frac{1}{12}+\frac{1}{12}=\frac{3}{12}=\frac{1}{4}\)
5407264
Jordan writes \(\frac{1}{4}+\frac{1}{4}+\frac{1}{4}=\frac{3}{12}\) because he adds the denominators as well as the numerators. a) Explain why the denominator should not change when equal-sized fourths are joined. b) Write the correct fraction for the unit-fraction sum.

Hints

- Ask what the denominator tells you about the size of each equal part. - Joining several fourth-sized parts does not cut those parts into a new size. - Count the number of unit fourths to determine the numerator of the sum.

Solution

1. Each addend is one fourth, so all three pieces have the same size. Joining them changes only how many fourths there are, not the size of each part. 2. There are three copies of \(\frac{1}{4}\), so the sum is \(\frac{3}{4}\), not \(\frac{3}{12}\).

Answer

a) The denominator stays \(4\) because every addend is still a fourth-sized part. b) \(\frac{1}{4}+\frac{1}{4}+\frac{1}{4}=\frac{3}{4}\)
5407294
For each expression, choose one classification: - repeated copies of the same unit fraction; - all terms are unit fractions, but they are not all the same unit fraction; - at least one term is not a unit fraction. For expressions in the first category, also write the total as one fraction. <table><tr><th>Label</th><th>Expression</th></tr><tr><td>A</td><td>\(\frac{1}{8}+\frac{1}{8}+\frac{1}{8}\)</td></tr><tr><td>B</td><td>\(\frac{1}{4}+\frac{1}{8}+\frac{1}{8}\)</td></tr><tr><td>C</td><td>\(\frac{2}{5}+\frac{1}{5}\)</td></tr><tr><td>D</td><td>\(\frac{1}{3}+\frac{1}{3}\)</td></tr><tr><td>E</td><td>\(\frac{1}{2}+\frac{1}{4}+\frac{1}{4}\)</td></tr></table>

Hints

- First check whether every numerator is \(1\). - If every term is a unit fraction, check whether all the denominators are the same. - Only when the same unit fraction repeats do you need to combine the count into one numerator.

Solution

1. A uses three copies of the same unit fraction \(\frac{1}{8}\), so it is in the first category and totals \(\frac{3}{8}\). 2. B contains only unit fractions, but it uses both \(\frac{1}{4}\) and \(\frac{1}{8}\), so it is in the second category. 3. C contains \(\frac{2}{5}\), whose numerator is not \(1\), so it is in the third category. 4. D uses two copies of the same unit fraction \(\frac{1}{3}\), so it is in the first category and totals \(\frac{2}{3}\). 5. E contains only unit fractions, but it uses \(\frac{1}{2}\) and \(\frac{1}{4}\), so it is in the second category.

Answer

A: repeated copies of the same unit fraction; \(\frac{3}{8}\) B: all terms are unit fractions, but they are not all the same unit fraction C: at least one term is not a unit fraction D: repeated copies of the same unit fraction; \(\frac{2}{3}\) E: all terms are unit fractions, but they are not all the same unit fraction
5407324
A unit-fraction decomposition is summarized in the table. <table><tr><th>Group</th><th>Number of \(\frac{1}{12}\) terms</th></tr><tr><td>A</td><td>3</td></tr><tr><td>B</td><td>1</td></tr><tr><td>C</td><td>5</td></tr></table> a) Write the complete expanded unit-fraction sum. b) Write the total as one fraction in simplest form. c) Which group contributes the greatest fraction of the whole, and what fraction does it contribute?

Hints

- Treat each table count as a number of copies of the same unit fraction. - Add the counts to determine the numerator of the total in twelfths. - For part c), compare the group counts because every term has the same size.

Solution

1. Group A contributes three \(\frac{1}{12}\) terms, group B contributes one, and group C contributes five. The complete expanded sum is \(\frac{1}{12}+\frac{1}{12}+\frac{1}{12}+\frac{1}{12}+\frac{1}{12}+\frac{1}{12}+\frac{1}{12}+\frac{1}{12}+\frac{1}{12}\). 2. The total is \(\frac{9}{12}=\frac{3}{4}\). 3. Group C has \(5\) copies, so it contributes \(\frac{5}{12}\), which is greater than group A's \(\frac{3}{12}\) and group B's \(\frac{1}{12}\).

Answer

a) \(\frac{1}{12}+\frac{1}{12}+\frac{1}{12}+\frac{1}{12}+\frac{1}{12}+\frac{1}{12}+\frac{1}{12}+\frac{1}{12}+\frac{1}{12}\) b) \(\frac{9}{12}=\frac{3}{4}\) c) Group C, \(\frac{5}{12}\)
5544204
Write \(\frac{3}{4}\) as exactly six identical unit fractions. What is the unit fraction?

Hints

- Six identical unit fractions will create an equivalent fraction with numerator \(6\). - Think about how the numerator \(3\) can become \(6\) without changing the fraction's value. - Apply the same scale factor to the denominator.

Solution

1. Six identical unit fractions combine to a fraction whose numerator is \(6\). 2. Find an equivalent fraction for \(\frac{3}{4}\) with numerator \(6\): multiply the numerator and denominator by \(2\). 3. \(\frac{3}{4}=\frac{6}{8}\), so the six identical terms are each \(\frac{1}{8}\).

Answer

\(\frac{1}{8}\)
5107054
In music, a \(\frac{4}{4}\) measure represents one whole measure. A half note has a value of \(\frac{1}{2}\), a quarter note has a value of \(\frac{1}{4}\), and an eighth note has a value of \(\frac{1}{8}\). A measure already contains one half note and one eighth note. a) What fraction of the measure is still unfilled? b) Give two different ways to fill the remaining part using only quarter notes and eighth notes.

Hints

- Think of one whole measure as eight equal eighth-note units. - Rewrite the half note in eighths. - How many eighths are missing from one whole measure? - Which combinations of quarter notes and eighth notes make that missing fraction?

Solution

1. The notes already use \(\frac{1}{2}+\frac{1}{8}=\frac{4}{8}+\frac{1}{8}=\frac{5}{8}\) of the measure. 2. For a), the unfilled part is \(1-\frac{5}{8}=\frac{3}{8}\). 3. For b), one quarter note and one eighth note fill \(\frac{2}{8}+\frac{1}{8}=\frac{3}{8}\). 4. Another way is three eighth notes: \(\frac{1}{8}+\frac{1}{8}+\frac{1}{8}=\frac{3}{8}\).

Answer

a) \(\frac{3}{8}\) b) One quarter note and one eighth note; or three eighth notes.
5114204
Find two different ways to represent \(\frac{2}{5}\) using distinct unit fractions. 1) Write it as the sum of exactly two different unit fractions. 2) Write it as the sum of exactly three different unit fractions.

Hints

- Start with a unit fraction smaller than \(\frac{2}{5}\), then find what remains. - For part 1), ask whether the remainder after your first choice is also a unit fraction. - For part 2), try decomposing a remaining fraction into two distinct unit fractions, and check that no denominator repeats.

Solution

1. For two unit fractions, subtract \(\frac{1}{3}\): \(\frac{2}{5}-\frac{1}{3}=\frac{6}{15}-\frac{5}{15}=\frac{1}{15}\). Therefore, \(\frac{2}{5}=\frac{1}{3}+\frac{1}{15}\). 2. For three unit fractions, begin with \(\frac{1}{4}\): \(\frac{2}{5}-\frac{1}{4}=\frac{8}{20}-\frac{5}{20}=\frac{3}{20}\). Since \(\frac{3}{20}=\frac{1}{10}+\frac{1}{20}\), one representation is \(\frac{2}{5}=\frac{1}{4}+\frac{1}{10}+\frac{1}{20}\).

Answer

1) \(\frac{2}{5}=\frac{1}{3}+\frac{1}{15}\) 2) \(\frac{2}{5}=\frac{1}{4}+\frac{1}{10}+\frac{1}{20}\)
5114234
Decompose \(\frac{5}{12}\) in two ways. a) Write \(\frac{5}{12}\) as a sum of five equal unit fractions. b) Find two different unit fractions whose sum is \(\frac{5}{12}\). Show your work.

Hints

- For part a), use the numerator to determine the number of twelfths. - For part b), look for unit fractions that can be rewritten with denominator \(12\). - Add using a common denominator to check your answer.

Solution

1. For a), \(\frac{5}{12}=\frac{1}{12}+\frac{1}{12}+\frac{1}{12}+\frac{1}{12}+\frac{1}{12}\). 2. For b), one choice is \(\frac{1}{4}+\frac{1}{6}\). Using a common denominator, \(\frac{1}{4}+\frac{1}{6}=\frac{3}{12}+\frac{2}{12}=\frac{5}{12}\). 3. Another valid choice is \(\frac{1}{3}+\frac{1}{12}=\frac{4}{12}+\frac{1}{12}=\frac{5}{12}\).

Answer

a) \(\frac{1}{12}+\frac{1}{12}+\frac{1}{12}+\frac{1}{12}+\frac{1}{12}\) b) For example, \(\frac{1}{4}+\frac{1}{6}\) or \(\frac{1}{3}+\frac{1}{12}\).
5114354
Consider the fraction \(\frac{7}{12}\). a) Find two different unit fractions whose sum is \(\frac{7}{12}\). b) Find a way to write \(\frac{7}{12}\) as a sum of three different unit fractions.

Hints

- Rewrite unit fractions with denominator \(12\). - For part b), try decomposing one unit fraction from part a) into two smaller unit fractions. - Check each sum using a common denominator.

Solution

1. For a), \(\frac{1}{3}+\frac{1}{4}=\frac{4}{12}+\frac{3}{12}=\frac{7}{12}\). Another valid answer is \(\frac{1}{2}+\frac{1}{12}\). 2. For b), \(\frac{1}{3}+\frac{1}{6}+\frac{1}{12}=\frac{4}{12}+\frac{2}{12}+\frac{1}{12}=\frac{7}{12}\).

Answer

a) For example, \(\frac{1}{3}+\frac{1}{4}\) or \(\frac{1}{2}+\frac{1}{12}\). b) For example, \(\frac{1}{3}+\frac{1}{6}+\frac{1}{12}\).
5406014
Nine identical unit fractions add to the shaded amount shown in the bar. What is the unit fraction?
Figure for problem 540601

Hints

- Read the shaded fraction from the bar. - Look for an equivalent fraction whose numerator matches the number of identical addends. - The denominator of that equivalent fraction tells the size of one unit fraction.

Solution

1. The bar shows \(3\) of \(4\) equal parts shaded, so the shaded amount is \(\frac{3}{4}\). 2. To express that amount with \(9\) equal unit-fraction terms, rename \(\frac{3}{4}\) with numerator \(9\): \(\frac{3}{4}=\frac{9}{12}\). 3. Therefore, the nine identical addends are copies of \(\frac{1}{12}\).

Answer

\(\frac{1}{12}\)
5406094
What is the smallest number of identical unit fractions that can add to the shaded amount shown? Name the unit fraction and write the sum.
Figure for problem 540609

Hints

- Read the shaded fraction from the bar and consider its simplest form. - In a repeated unit-fraction sum, the numerator counts the number of identical terms. - Ask what happens to that numerator when you make an equivalent fraction with more equal parts.

Solution

1. The bar shows \(\frac{3}{4}\). 2. In simplest form, \(\frac{3}{4}\) means \(3\) copies of the unit fraction \(\frac{1}{4}\). 3. Any equivalent fraction with a different denominator would multiply the numerator \(3\) by a whole number and therefore use more than \(3\) identical unit-fraction copies. 4. The smallest possible number of terms is \(3\): \(\frac{1}{4}+\frac{1}{4}+\frac{1}{4}\).

Answer

\(3\) terms: \(\frac{1}{4}+\frac{1}{4}+\frac{1}{4}\)
5407174
The bar shows one whole divided into three colored unit-fraction amounts. Make three different four-term unit-fraction decompositions of \(1\) by choosing one colored term and splitting it into two equal unit fractions. For each decomposition, state which original unit fraction you split.
Figure for problem 540717

Hints

- Read each colored segment as a fraction of the twelve equal parts. - Choose one colored unit fraction and imagine dividing that amount into two equal pieces. - Check that each new expression has four unit-fraction terms and still makes one whole.

Solution

1. The blue part is \(\frac{6}{12}=\frac{1}{2}\). Splitting it into two equal parts gives \(\frac{1}{4}+\frac{1}{4}\), so \(1=\frac{1}{4}+\frac{1}{4}+\frac{1}{3}+\frac{1}{6}\). 2. The orange part is \(\frac{4}{12}=\frac{1}{3}\). Splitting it into two equal parts gives \(\frac{1}{6}+\frac{1}{6}\), so \(1=\frac{1}{2}+\frac{1}{6}+\frac{1}{6}+\frac{1}{6}\). 3. The green part is \(\frac{2}{12}=\frac{1}{6}\). Splitting it into two equal parts gives \(\frac{1}{12}+\frac{1}{12}\), so \(1=\frac{1}{2}+\frac{1}{3}+\frac{1}{12}+\frac{1}{12}\).

Answer

Split \(\frac{1}{2}\): \(\frac{1}{4}+\frac{1}{4}+\frac{1}{3}+\frac{1}{6}\) Split \(\frac{1}{3}\): \(\frac{1}{2}+\frac{1}{6}+\frac{1}{6}+\frac{1}{6}\) Split \(\frac{1}{6}\): \(\frac{1}{2}+\frac{1}{3}+\frac{1}{12}+\frac{1}{12}\)
5407204
Consider the fractions \(\frac{1}{12},\frac{2}{12},\frac{3}{12},\ldots,\frac{11}{12}\). List every one that is equivalent to a unit fraction. For each one, name the equivalent unit fraction.

Hints

- A unit fraction has numerator \(1\). - Simplify each candidate only as far as needed to decide whether its numerator can become \(1\). - Look for a common factor shared by the numerator and \(12\).

Solution

1. A unit fraction has numerator \(1\), so each fraction must simplify to a fraction with numerator \(1\). 2. \(\frac{1}{12}\) is already a unit fraction. Also, \(\frac{2}{12}=\frac{1}{6}\), \(\frac{3}{12}=\frac{1}{4}\), \(\frac{4}{12}=\frac{1}{3}\), and \(\frac{6}{12}=\frac{1}{2}\). 3. The remaining fractions from \(\frac{5}{12}\) through \(\frac{11}{12}\) do not simplify to a numerator of \(1\).

Answer

\(\frac{1}{12}=\frac{1}{12}\), \(\frac{2}{12}=\frac{1}{6}\), \(\frac{3}{12}=\frac{1}{4}\), \(\frac{4}{12}=\frac{1}{3}\), \(\frac{6}{12}=\frac{1}{2}\)
5407214
Camden writes \(\frac{3}{4}=\frac{2}{4}+\frac{1}{4}\) and calls both addends unit fractions because both have denominator \(4\). a) Explain Camden's mistake. b) Rewrite \(\frac{3}{4}\) in two valid ways using only unit fractions.

Hints

- For part a), use the definition of a unit fraction, not only the denominator. - For part b), think about an equivalent unit fraction for \(\frac{2}{4}\). - Find a second decomposition by treating \(\frac{3}{4}\) as copies of one unit fraction.

Solution

1. A unit fraction must have numerator \(1\). Therefore, \(\frac{2}{4}\) is not a unit fraction, even though it is equivalent to \(\frac{1}{2}\). 2. One valid rewrite is \(\frac{3}{4}=\frac{1}{2}+\frac{1}{4}\). 3. Another valid rewrite is \(\frac{3}{4}=\frac{1}{4}+\frac{1}{4}+\frac{1}{4}\).

Answer

a) \(\frac{2}{4}\) is not a unit fraction because its numerator is not \(1\). b) \(\frac{3}{4}=\frac{1}{2}+\frac{1}{4}\); \(\frac{3}{4}=\frac{1}{4}+\frac{1}{4}+\frac{1}{4}\)
5407234
The bar shows one whole separated into three colored unit-fraction amounts. a) Express each colored amount in twelfths. How many unit twelfths come from each amount? b) Rewrite the entire decomposition using only unit twelfths, and state the total number of terms.
Figure for problem 540723

Hints

- Use the twelve equal sections of the bar as the common unit. - Count how many twelfths belong to each color before combining them. - The total number of unit fractions is the sum of the three color counts.

Solution

1. The blue amount is \(\frac{6}{12}=\frac{1}{2}\), so it contributes six copies of \(\frac{1}{12}\). 2. The orange amount is \(\frac{4}{12}=\frac{1}{3}\), so it contributes four copies of \(\frac{1}{12}\). 3. The green amount is \(\frac{2}{12}=\frac{1}{6}\), so it contributes two copies of \(\frac{1}{12}\). 4. Altogether there are \(6+4+2=12\) copies of \(\frac{1}{12}\), which make \(1\).

Answer

a) Blue: \(6\) twelfths; orange: \(4\) twelfths; green: \(2\) twelfths b) Twelve copies of \(\frac{1}{12}\); total \(1\)
5407354
A decomposition tree begins with \(1\). First, the whole splits into \(\frac{1}{2}+\frac{1}{2}\). Next, one half splits into \(\frac{1}{3}+\frac{1}{6}\). Finally, the sixth splits into \(\frac{1}{12}+\frac{1}{12}\). a) List the final leaf terms. b) How many leaves are there? c) Verify their total.

Hints

- For part a), replace a term only when the tree says that term splits. - Terms that do not split remain in the final leaf list. - For parts b) and c), count the final terms and verify them with twelfths.

Solution

1. One original half remains a leaf: \(\frac{1}{2}\). 2. The other half is replaced by \(\frac{1}{3}\) and \(\frac{1}{6}\), and the sixth is then replaced by two twelfths. 3. The final leaves are \(\frac{1}{2},\frac{1}{3},\frac{1}{12},\frac{1}{12}\), for four leaves. 4. Their total is \(\frac{6}{12}+\frac{4}{12}+\frac{1}{12}+\frac{1}{12}=1\).

Answer

a) \(\frac{1}{2},\frac{1}{3},\frac{1}{12},\frac{1}{12}\) b) \(4\) leaves c) \(\frac{6}{12}+\frac{4}{12}+\frac{1}{12}+\frac{1}{12}=1\)
5407384
Use the bar to explain how the shaded fraction can be written as a sum of copies of one unit fraction. Then explain in words why the same idea works for any proper fraction: what does its numerator count, and what does its denominator tell you?
Figure for problem 540738

Hints

- Count all equal parts in the bar to identify the unit fraction. - Count the shaded parts to identify how many copies of that unit fraction are used. - Generalize from what the two numbers in a fraction tell you about equal parts.

Solution

1. The bar has \(8\) equal parts, so one part is \(\frac{1}{8}\). Five parts are shaded, so the shaded fraction is \(\frac{5}{8}\). 2. Therefore, \(\frac{5}{8}=\frac{1}{8}+\frac{1}{8}+\frac{1}{8}+\frac{1}{8}+\frac{1}{8}\). 3. In any fraction, the denominator tells the size of one equal part, so it determines the unit fraction. The numerator tells how many of those equal parts are counted.

Answer

The model shows \(\frac{5}{8}=\frac{1}{8}+\frac{1}{8}+\frac{1}{8}+\frac{1}{8}+\frac{1}{8}\). In general, the denominator names the unit fraction and the numerator tells how many copies of that unit fraction are present.
5114384
The fraction \(\frac{3}{10}\) has these two unit-fraction decompositions: Method A: \(\frac{1}{4}+\frac{1}{20}\) Method B: \(\frac{1}{5}+\frac{1}{10}\) a) Verify that both decompositions are correct. b) In the greedy method, you begin with the greatest unit fraction that does not exceed the original fraction. Which method follows the greedy rule? Explain.

Hints

- Verify each sum using a common denominator. - Compare the first unit fractions in the two methods. - Check the next larger unit fraction to determine whether it would exceed \(\frac{3}{10}\).

Solution

1. For Method A, \(\frac{1}{4}+\frac{1}{20}=\frac{5}{20}+\frac{1}{20}=\frac{6}{20}=\frac{3}{10}\). 2. For Method B, \(\frac{1}{5}+\frac{1}{10}=\frac{2}{10}+\frac{1}{10}=\frac{3}{10}\). 3. The greatest unit fraction not exceeding \(\frac{3}{10}\) is \(\frac{1}{4}\): \(\frac{1}{3}>\frac{3}{10}\), while \(\frac{1}{4}<\frac{3}{10}\). Therefore, Method A follows the greedy rule.

Answer

a) Both methods are correct. b) Method A follows the greedy rule because \(\frac{1}{4}\) is the greatest unit fraction less than \(\frac{3}{10}\).
5114394
In the greedy method for unit fractions, choose the greatest unit fraction that does not exceed the current fraction, subtract it, and repeat with the remainder. Use the greedy method to write \(\frac{3}{14}\) as a sum of unit fractions. 1) Find the greatest unit fraction \(\frac{1}{k}\) that is less than \(\frac{3}{14}\). 2) Subtract that unit fraction and write the complete decomposition.

Hints

- Estimate the reciprocal of \(\frac{3}{14}\) to find the first denominator. - Use a common denominator to subtract the fractions. - Check whether the remainder is a unit fraction.

Solution

1. Since \(14\div3\approx4.67\), the smallest integer denominator that gives a unit fraction less than \(\frac{3}{14}\) is \(5\). Thus, the first term is \(\frac{1}{5}\). 2. Subtract: \(\frac{3}{14}-\frac{1}{5}=\frac{15}{70}-\frac{14}{70}=\frac{1}{70}\). 3. Therefore, \(\frac{3}{14}=\frac{1}{5}+\frac{1}{70}\).

Answer

\(\frac{3}{14}=\frac{1}{5}+\frac{1}{70}\)
5114414
A unit fraction has a numerator of \(1\). Find two ways to write \(\frac{1}{4}\) as a sum of two distinct unit fractions. Verify each sum.

Hints

- Test unit fractions slightly less than \(\frac{1}{4}\). - After choosing one term, subtract it from \(\frac{1}{4}\) to find the other. - The two unit fractions in each sum must be different.

Solution

1. Try unit fractions just less than \(\frac{1}{4}\). 2. Starting with \(\frac{1}{5}\), the remainder is \(\frac{1}{4}-\frac{1}{5}=\frac{1}{20}\). Thus, \(\frac{1}{4}=\frac{1}{5}+\frac{1}{20}\). 3. Starting with \(\frac{1}{6}\), the remainder is \(\frac{1}{4}-\frac{1}{6}=\frac{1}{12}\). Thus, \(\frac{1}{4}=\frac{1}{6}+\frac{1}{12}\). 4. Verify: \(\frac{1}{5}+\frac{1}{20}=\frac{4}{20}+\frac{1}{20}=\frac{1}{4}\), and \(\frac{1}{6}+\frac{1}{12}=\frac{2}{12}+\frac{1}{12}=\frac{1}{4}\).

Answer

1) \(\frac{1}{4}=\frac{1}{5}+\frac{1}{20}\) 2) \(\frac{1}{4}=\frac{1}{6}+\frac{1}{12}\)
5114454
The greedy method writes a fraction as a sum of unit fractions by repeatedly subtracting the greatest unit fraction that is less than or equal to the current remainder. Apply the greedy method to \(\frac{4}{5}\) until you obtain a sum of three different unit fractions. Show your steps.

Hints

- At each stage, choose the greatest unit fraction that does not exceed the current amount. - Use common denominators for each subtraction. - Stop when the remainder is a unit fraction.

Solution

1. The greatest unit fraction less than \(\frac{4}{5}\) is \(\frac{1}{2}\). 2. Subtract: \(\frac{4}{5}-\frac{1}{2}=\frac{8}{10}-\frac{5}{10}=\frac{3}{10}\). 3. The greatest unit fraction less than \(\frac{3}{10}\) is \(\frac{1}{4}\), because \(\frac{1}{3}>\frac{3}{10}\). 4. Subtract: \(\frac{3}{10}-\frac{1}{4}=\frac{6}{20}-\frac{5}{20}=\frac{1}{20}\). 5. Therefore, \(\frac{4}{5}=\frac{1}{2}+\frac{1}{4}+\frac{1}{20}\).

Answer

\(\frac{4}{5}=\frac{1}{2}+\frac{1}{4}+\frac{1}{20}\)
5118404
A unit fraction has a numerator of \(1\). Write \(\frac{3}{4}\) as a sum of exactly three different unit fractions.

Hints

- Start with a large unit fraction that is less than \(\frac{3}{4}\). - Subtract it to find the remainder. - Split the remainder into two different unit fractions.

Solution

1. Begin with \(\frac{1}{2}\): \(\frac{3}{4}-\frac{1}{2}=\frac{1}{4}\). 2. Decompose the remainder: \(\frac{1}{4}=\frac{1}{5}+\frac{1}{20}\). 3. Therefore, \(\frac{3}{4}=\frac{1}{2}+\frac{1}{5}+\frac{1}{20}\). 4. Another valid answer is \(\frac{3}{4}=\frac{1}{2}+\frac{1}{6}+\frac{1}{12}\).

Answer

One possible answer is \(\frac{3}{4}=\frac{1}{2}+\frac{1}{5}+\frac{1}{20}\).
5406104
Can \(\frac{2}{3}\) be written as exactly five identical unit fractions? Explain why or why not using equivalent fractions.

Hints

- If five identical unit fractions are combined, what number would count the copies in the numerator? - List a few numerators of fractions equivalent to \(\frac{2}{3}\). - Decide whether a numerator of \(5\) can occur in that pattern.

Solution

1. Five identical unit fractions would combine into one fraction whose numerator is \(5\), because there would be five equal unit-fraction copies. 2. Equivalent fractions for \(\frac{2}{3}\) are made by multiplying the numerator and denominator by the same whole number. Their numerators are \(2,4,6,8,\ldots\). 3. Since \(5\) is not one of those possible numerators, no equivalent fraction for \(\frac{2}{3}\) can represent exactly five identical unit-fraction copies.

Answer

No. \(\frac{2}{3}\) cannot be written as exactly five identical unit fractions.
5407374
The bar shows one whole made from three colored unit-fraction pieces. A split replaces one unit fraction by two equal unit fractions, so the value stays the same. a) Starting from the decomposition shown, perform four splits and give one possible final decomposition. b) How many terms must every four-split result have? Explain.
Figure for problem 540737

Hints

- Read the three original unit fractions from the colored bar before making any split. - A split replaces one unit fraction by two equal smaller unit fractions without changing the total value. - Track both the number of splits and the number of terms after each split.

Solution

1. The bar represents \(\frac{1}{2}+\frac{1}{4}+\frac{1}{4}=1\), which starts with three terms. 2. Split \(\frac{1}{2}\) into \(\frac{1}{4}+\frac{1}{4}\). There are now four quarter terms. 3. Split one \(\frac{1}{4}\) into \(\frac{1}{8}+\frac{1}{8}\). 4. Split a second \(\frac{1}{4}\) into \(\frac{1}{8}+\frac{1}{8}\), then split a third \(\frac{1}{4}\) the same way. After four splits total, one possible result is \(\frac{1}{4}+\frac{1}{8}+\frac{1}{8}+\frac{1}{8}+\frac{1}{8}+\frac{1}{8}+\frac{1}{8}=1\). 5. Each split replaces one term by two, so every split increases the term count by exactly \(1\). Starting with \(3\) terms, four splits always produce \(7\) terms.

Answer

a) One possible result is \(\frac{1}{4}+\frac{1}{8}+\frac{1}{8}+\frac{1}{8}+\frac{1}{8}+\frac{1}{8}+\frac{1}{8}=1\). b) Every four-split result has \(7\) terms.

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