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Angles as fractions of a circle

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5543394
One full turn measures \(360^\circ\). What fraction of a full turn is a \(1^\circ\) turn?

Hints

- Think of the full turn as being split into equal one-degree parts. - How many one-degree parts make the whole turn? - The fraction for one equal part has \(1\) in the numerator.

Solution

1. A full turn is divided into \(360\) equal one-degree turns. 2. One of those equal parts is \(\frac{1}{360}\) of the full turn.

Answer

\(\frac{1}{360}\) of a full turn
5543404
Tessa turns through \(\frac{3}{4}\) of a full turn. How many degrees does Tessa turn?

Hints

- Compare the turn with familiar quarter-, half-, and full-turn benchmarks. - A full turn can be split into four equal quarter-turns. - The requested turn uses three of those four equal parts.

Solution

1. A full turn is \(360^\circ\). 2. Three quarters of \(360^\circ\) is \(\frac{3}{4} \times 360^\circ = 270^\circ\).

Answer

\(270^\circ\)
5189114
A large pizza is cut into equal slices. Find the angle at the center of one slice when the pizza is divided into: a) \(4\) slices b) \(6\) slices c) \(9\) slices d) \(15\) slices

Hints

- A full circle measures \(360^\circ\). - Equal slices have equal central angles. - For a larger number of slices, think of the slice angle as a missing factor that must make \(360^\circ\).

Solution

1. A full circle measures \(360^\circ\). 2. For \(4\) slices, \(360^\circ \div 4=90^\circ\). 3. For \(6\) slices, \(360^\circ \div 6=60^\circ\). 4. For \(9\) slices, \(360^\circ \div 9=40^\circ\). 5. For \(15\) slices, use \(15 \times 24^\circ=360^\circ\), so one slice has a \(24^\circ\) central angle.

Answer

a) \(90^\circ\) b) \(60^\circ\) c) \(40^\circ\) d) \(24^\circ\)
5189134
Use the numbered clock face shown. The numbers \(1\) through \(12\) are evenly spaced. a) Through what angle does the minute hand turn as it moves from \(12\) to \(1\)? b) What is the smaller angle from \(12\) to \(4\)? c) What is the angle from \(12\) to \(6\)? Name this type of angle.
Figure for problem 518913

Hints

- The equal hour spaces divide one full turn into \(12\) equal parts. - Count the number of equal spaces from \(12\) to each target number. - For part c, compare the turn with half of a full turn.

Solution

1. The \(12\) equal clock sections make a full turn, so each section is \(360^\circ \div 12 = 30^\circ\). 2. From \(12\) to \(1\) is one section: \(30^\circ\). 3. From \(12\) to \(4\) is four sections: \(4 \times 30^\circ = 120^\circ\). 4. From \(12\) to \(6\) is six sections: \(6 \times 30^\circ = 180^\circ\), a straight angle.

Answer

a) \(30^\circ\) b) \(120^\circ\) c) \(180^\circ\), a straight angle
5189604
The three clocks are shown in panels a), b), and c). Find the smaller angle between the hour hand and minute hand on each clock. Classify each angle as acute, right, or obtuse.
Figure for problem 518960

Hints

- Determine the angle represented by one hour-to-hour space. - Count the smaller number of spaces between the hands in each panel. - Compare each resulting angle with \(90^\circ\).

Solution

1. The \(12\) equal hour sections make a full turn, so each section measures \(30^\circ\). 2. In a), the hands are two sections apart: \(60^\circ\), an acute angle. 3. In b), the hands are five sections apart: \(150^\circ\), an obtuse angle. 4. In c), the smaller separation is three sections: \(90^\circ\), a right angle.

Answer

a) \(60^\circ\), acute b) \(150^\circ\), obtuse c) \(90^\circ\), right
5210234
The two clocks show the starting and ending positions of an hour hand. Through what angle does the hour hand turn from panel a) to panel b)?
Figure for problem 521023

Hints

- Count the equal hour spaces from the starting hand position to the ending hand position. - One full turn is divided into \(12\) equal hour spaces. - Use the number of spaces and the size of one space to find the turn.

Solution

1. The hour hand moves through \(5\) equal hour spaces. 2. Each hour space is \(360^\circ \div 12 = 30^\circ\). 3. The turn is \(5 \times 30^\circ = 150^\circ\).

Answer

\(150^\circ\)
5377864
In each diagram, the spokes divide the full circle into equal parts. Starting at spoke \(s\) and moving counterclockwise to spoke \(e\), what fraction of a full turn is shown? Write each fraction in simplest form.
Figure for problem 537786

Hints

- Count how many equal sectors make the complete circle in each panel. - Count how many of those sectors lie on the counterclockwise turn from \(s\) to \(e\). - Use sectors traveled over total sectors, then simplify when possible.

Solution

1. In a), the circle has \(4\) equal parts and the turn covers \(1\), so the turn is \(\frac{1}{4}\). 2. In b), the circle has \(6\) equal parts and the turn covers \(2\), so \(\frac{2}{6}=\frac{1}{3}\). 3. In c), the circle has \(8\) equal parts and the turn covers \(3\), so the turn is \(\frac{3}{8}\). 4. In d), the circle has \(3\) equal parts and the turn covers \(2\), so the turn is \(\frac{2}{3}\).

Answer

a) \(\frac{1}{4}\) b) \(\frac{1}{3}\) c) \(\frac{3}{8}\) d) \(\frac{2}{3}\)
5377964
The path passes through \(A\), \(B\), \(C\), \(D\), and \(E\). For each interior angle \(\angle ABC\), \(\angle BCD\), and \(\angle CDE\), write the angle as a fraction of a full turn. Which one is not a quarter-turn?
Figure for problem 537796

Hints

- Look at the two segments that meet at each named vertex. - Compare a square corner and a straight angle with a complete turn. - Give a fraction for every named angle before deciding which one differs.

Solution

1. At \(B\), the horizontal and vertical segments form \(\frac{1}{4}\) of a full turn. 2. At \(C\), the two path segments form a straight angle, which is \(\frac{1}{2}\) of a full turn. 3. At \(D\), the vertical and horizontal segments form \(\frac{1}{4}\) of a full turn. 4. Therefore, \(\angle BCD\) is the one that is not a quarter-turn.

Answer

\(\angle ABC=\frac{1}{4}\) turn \(\angle BCD=\frac{1}{2}\) turn \(\angle CDE=\frac{1}{4}\) turn \(\angle BCD\) is not a quarter-turn.
5378104
Three segments meet at \(B\). Express each smaller angle as a fraction of a full turn: a) the angle between \(\overline{BA}\) and \(\overline{BC}\) b) the angle between \(\overline{BC}\) and \(\overline{BD}\) c) the angle between \(\overline{BA}\) and \(\overline{BD}\)
Figure for problem 537810

Hints

- Compare each pair separately; do not assume all three angles are equal. - A quarter-turn and a half-turn are benchmark fractions of one complete turn. - For the last pair, notice whether the two segments point in opposite directions.

Solution

1. The directions of \(\overline{BA}\) and \(\overline{BC}\) differ by a quarter-turn, so a) is \(\frac{1}{4}\). 2. The directions of \(\overline{BC}\) and \(\overline{BD}\) also differ by a quarter-turn, so b) is \(\frac{1}{4}\). 3. The directions of \(\overline{BA}\) and \(\overline{BD}\) are opposite, so c) is a half-turn, \(\frac{1}{2}\).

Answer

a) \(\frac{1}{4}\) of a full turn b) \(\frac{1}{4}\) of a full turn c) \(\frac{1}{2}\) of a full turn
5378254
A robot follows the route \(A\to B\to C\to D\to E\). At \(B\), \(C\), and \(D\), it makes the smaller turn needed to follow the next segment. a) What fraction of a full turn does it make at each of the three corners? b) What fraction of a full turn does it make in total across the three corners?
Figure for problem 537825

Hints

- Examine the change in direction at each labeled corner, not the lengths of the segments. - Express one square-corner turn as a fraction of a complete turn. - Combine the three equal turn fractions for the total.

Solution

1. Each change in direction is a quarter-turn, so the robot turns \(\frac{1}{4}\) of a full turn at \(B\), \(C\), and \(D\). 2. The total turning is \(\frac{1}{4}+\frac{1}{4}+\frac{1}{4}=\frac{3}{4}\) of a full turn.

Answer

a) \(\frac{1}{4}\) turn at each of \(B\), \(C\), and \(D\) b) \(\frac{3}{4}\) of a full turn in total
5522374
The circle shown is divided into \(8\) equal sectors by spokes from \(O\). Starting at spoke \(a\) and moving counterclockwise to spoke \(d\), what fraction of a full turn is made, and what is the angle measure in degrees?
Figure for problem 552237

Hints

- Count the equal sectors swept out from spoke \(a\) to spoke \(d\) in the stated direction. - Write the number of swept sectors over the total number of sectors to form the fraction of a full turn. - Divide a full turn equally among the sectors, then scale that angle by the number swept out.

Solution

1. The counterclockwise turn from spoke \(a\) to spoke \(d\) covers \(3\) of the \(8\) equal sectors, so it is \(\frac{3}{8}\) of a full turn. 2. Each sector measures \(360^\circ\div8=45^\circ\). 3. Three sectors measure \(3\times45^\circ=135^\circ\).

Answer

\(\frac{3}{8}\) of a full turn; \(135^\circ\)
5543414
A wheel rotates through \(\frac{5}{12}\) of a full turn. How many degrees is this rotation?

Hints

- Think of the full turn as \(12\) equal parts. - Determine the degree measure of one of those equal parts. - Then account for the number of parts named by the numerator.

Solution

1. A full turn is \(360^\circ\), so one twelfth is \(360^\circ \div 12 = 30^\circ\). 2. Five twelfths is \(5 \times 30^\circ = 150^\circ\).

Answer

\(150^\circ\)
5543424
An angle measures \(120^\circ\). What fraction of a full turn is this angle? Write the fraction in simplest form.

Hints

- Put the angle measure over the degree measure of one full turn. - Then simplify the fraction without changing its value. - Check that the result is less than one full turn.

Solution

1. Compare the angle with a full turn: \(\frac{120}{360}\). 2. Simplify the fraction: \(\frac{120}{360} = \frac{1}{3}\).

Answer

\(\frac{1}{3}\) of a full turn
5543434
The diagram shows a robot's starting direction \(s\), its direction \(a\) after the first clockwise turn, and its final direction \(b\) after the second clockwise turn. a) What fraction of a full turn is the first turn from \(s\) to \(a\)? b) What fraction of a full turn is the second turn from \(a\) to \(b\)? c) What fraction of a full turn does the robot turn altogether, and how many degrees is that?
Figure for problem 554343

Hints

- Use the circle and the labeled rays to judge each clockwise change in direction. - Compare each turn with benchmark parts of a complete turn. - Combine the two turn fractions only after identifying them from the diagram.

Solution

1. From \(s\) to \(a\), the robot turns one quarter of the circle, so the first turn is \(\frac{1}{4}\). 2. From \(a\) to \(b\), the robot turns halfway around the circle, so the second turn is \(\frac{1}{2}\). 3. The total is \(\frac{1}{4}+\frac{1}{2}=\frac{3}{4}\) of a full turn. 4. Three quarters of \(360^\circ\) is \(270^\circ\).

Answer

a) \(\frac{1}{4}\) of a full turn b) \(\frac{1}{2}\) of a full turn c) \(\frac{3}{4}\) of a full turn, or \(270^\circ\)
5123764
a) An angle is \(\frac{4}{9}\) of a straight angle. Find its measure in degrees. b) What fraction of a full turn is \(135^\circ\)? Write the fraction in simplest form.

Hints

- A straight angle measures \(180^\circ\), and a full turn measures \(360^\circ\). - For part a), first find one ninth of the straight angle. - For part b), look for an angle size that makes equal groups in both \(135^\circ\) and \(360^\circ\).

Solution

1. A straight angle measures \(180^\circ\). One ninth of \(180^\circ\) is \(20^\circ\), so \(\frac{4}{9}\) of it is \(4 \times 20^\circ=80^\circ\). 2. A full turn measures \(360^\circ\). 3. Think in \(45^\circ\) parts: \(135^\circ=3 \times 45^\circ\) and \(360^\circ=8 \times 45^\circ\). 4. Therefore, \(135^\circ\) is \(\frac{3}{8}\) of a full turn.

Answer

a) \(80^\circ\) b) \(\frac{3}{8}\) of a full turn
5189124
The passenger cars on a Ferris wheel are evenly spaced around the wheel. a) A Ferris wheel has \(12\) cars. Find the central angle between two neighboring cars. b) A smaller Ferris wheel has a central angle of \(45^\circ\) between neighboring cars. How many cars does it have?

Hints

- Think of the wheel as a full \(360^\circ\) turn divided into equal sections. - In part a), find the missing angle in \(12 \times ?=360^\circ\). - In part b), find how many \(45^\circ\) sections make \(360^\circ\).

Solution

1. A full circle measures \(360^\circ\). 2. Since \(12 \times 30^\circ=360^\circ\), the angle between neighboring cars in part a) is \(30^\circ\). 3. Since \(8 \times 45^\circ=360^\circ\), the smaller wheel has \(8\) cars.

Answer

a) \(30^\circ\) b) \(8\) cars
5189434
Use the numbered clock face shown. The minute hand makes one full turn in \(60\) minutes. a) Through what angle does it turn in \(10\) minutes? b) How many minutes pass while it turns through \(150^\circ\)? c) The minute hand moves from \(2\) to \(6\). Through what angle does it turn?
Figure for problem 518943

Hints

- Connect \(60\) equal one-minute turns with one full turn. - Use the one-minute turn in both forward and reverse directions. - For part c, count equal spaces on the numbered clock face.

Solution

1. Sixty equal one-minute turns make \(360^\circ\), so the minute hand turns \(6^\circ\) each minute. 2. In \(10\) minutes, it turns \(10 \times 6^\circ = 60^\circ\). 3. A turn of \(150^\circ\) takes \(150 \div 6 = 25\) minutes. 4. Moving from \(2\) to \(6\) covers four hour spaces; each is \(30^\circ\), so the turn is \(120^\circ\).

Answer

a) \(60^\circ\) b) \(25\) minutes c) \(120^\circ\)
5543444
Mia says, “A \(45^\circ\) angle is \(\frac{1}{4}\) of a full turn because \(45\) is a common angle measure.” Explain why Mia is incorrect and give the correct fraction of a full turn.

Hints

- Compare \(45^\circ\) with the full \(360^\circ\) turn. - Recall the degree measure of a quarter-turn as a benchmark. - Form a fraction using the angle measure and the full-turn measure, then simplify.

Solution

1. A full turn is \(360^\circ\), so the fraction is \(\frac{45}{360}\). 2. Simplify: \(\frac{45}{360} = \frac{1}{8}\). 3. A quarter-turn is \(90^\circ\), not \(45^\circ\).

Answer

Mia is incorrect. A \(45^\circ\) angle is \(\frac{1}{8}\) of a full turn.

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