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Lines of symmetry

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5506604
Which figure does not have a line of symmetry?
Figure for problem 550660

Hints

- Imagine folding each figure into two matching halves. - A symmetry fold must match every vertex and side. - Check more than just the top point.

Solution

1. Figure a) can be folded down the middle so its left and right sides match exactly. 2. Figure b) has unequal side positions, so no fold makes the two halves match. Therefore b) does not have a line of symmetry.

Answer

b)
5506614
Each drawing shows the same isosceles triangle with a proposed fold line. Which proposed line is a line of symmetry?
Figure for problem 550661

Hints

- A valid fold must make every edge on one side land on an edge on the other side. - Look for the midpoint of the base. - Test the proposed lines by imagining an actual fold.

Solution

1. In a), the vertical line passes through the top vertex and the midpoint of the base, dividing the triangle into matching halves. 2. The horizontal line in b) does not match the top of the triangle with the base. 3. The slanted line in c) does not divide the triangle into mirror-image halves. Therefore a) is correct.

Answer

a)
5506624
Match each figure to its number of lines of symmetry: \(0\), \(1\), or \(2\).
Figure for problem 550662

Hints

- Try possible folds through the center of each figure. - A line counts only if every point has a matching point across it. - Different figures can have different numbers of valid folds.

Solution

1. Figure a) is a scalene triangle, so it has \(0\) lines of symmetry. 2. Figure b) is an isosceles triangle, so it has \(1\) line of symmetry through its top vertex and the midpoint of its base. 3. Figure c) is a non-square rectangle, so it has \(2\) lines of symmetry: one vertical and one horizontal through its center.

Answer

a) \(0\) b) \(1\) c) \(2\)
5123944
Identify quadrilaterals from their lines of symmetry. a) Which quadrilateral has exactly two lines of symmetry, both passing through opposite vertices? b) Which quadrilateral has exactly two lines of symmetry, both passing through the midpoints of opposite sides? c) Which quadrilateral has four lines of symmetry? Describe where those lines are located.

Hints

- Imagine folding each quadrilateral so that its edges match exactly. - Picture the quadrilaterals and test possible fold lines. - Distinguish lines through vertices from lines through side midpoints. - Which quadrilateral has the greatest number of matching fold lines?

Solution

1. A rhombus that is not a square has exactly two lines of symmetry: its diagonals. 2. A rectangle that is not a square has exactly two lines of symmetry. Each passes through the midpoints of a pair of opposite sides. 3. A square has four lines of symmetry: its two diagonals and the two lines through the midpoints of opposite sides.

Answer

a) A rhombus that is not a square. b) A rectangle that is not a square. c) A square. Its lines of symmetry are the two diagonals and the two lines through the midpoints of opposite sides.
5189944
Compare the line symmetry of a non-square rectangle and a square. a) How many lines of symmetry does a non-square rectangle have? Describe them. b) How many lines of symmetry does a square have? c) Why does a square have more lines of symmetry?

Hints

- Imagine folding each shape so its edges match. - Compare folds through side midpoints with folds through opposite vertices. - Consider what changes when all four sides are congruent.

Solution

1. A non-square rectangle has \(2\) lines of symmetry. Each passes through the midpoints of a pair of opposite sides. 2. A square has \(4\) lines of symmetry. 3. A square has the same two midpoint lines as a rectangle, and its two diagonals are also lines of symmetry because all four sides are congruent.

Answer

a) \(2\); they pass through the midpoints of opposite sides. b) \(4\) c) The square’s diagonals are also lines of symmetry.
5354644
The pentagon is shown on a geoboard. Is the figure line-symmetric? If so, how many lines of symmetry does it have, and where are they?
Figure for problem 535464

Hints

- Imagine folding the figure so that its edges match exactly. - Look for pairs of vertices that are the same distance from a possible fold line. - Test vertical, horizontal, and diagonal fold lines.

Solution

1. A vertical fold through the top vertex and the midpoint of the bottom side maps the left half of the pentagon onto the right half. 2. No horizontal or diagonal fold maps the figure onto itself. 3. Therefore the pentagon has exactly one line of symmetry.

Answer

Yes. It has exactly one line of symmetry: the vertical line through the top vertex and the midpoint of the bottom side.
5372284
Original figure O is shown on one side of the red line. Which image—1, 2, or 3—shows the matching half that would make the red line a line of symmetry for the combined figure? Each grid cell represents 1 unit. Compare the orientation and perpendicular distance from the red line.
Figure for problem 537228

Hints

- Imagine folding along the red line. - Matching points must be the same perpendicular distance from the fold line. - Check that the matching half has the reversed orientation. - A vertical shift prevents the halves from matching.

Solution

1. For the red line to be a line of symmetry, every point in the matching half must be the same perpendicular distance from the red line as its partner in figure O. 2. Image 1 has the correct overall position, but it keeps the original orientation instead of reflecting it across the red line. 3. Image 2 reverses the orientation and places every corresponding point the same distance from the red line on the opposite side. 4. Image 3 is shifted 1 unit upward, so the two halves would not match when folded along the red line.

Answer

Image 2
5506634
The dashed line is proposed as a line of symmetry for the kite-shaped figure. Is it a line of symmetry? Explain.
Figure for problem 550663

Hints

- Check where each vertex would land after a fold. - Compare the left and right vertices with the dashed line. - A valid symmetry line must match the entire boundary, not just one pair of points.

Solution

1. The dashed line passes through the top and bottom vertices. 2. The left vertex and right vertex are the same distance from the dashed line and lie at the same height. 3. Folding along the dashed line matches all four sides, so it is a line of symmetry.

Answer

Yes. Folding along the dashed vertical line maps the left half exactly onto the right half.
5506644
The dashed vertical line is the fold line. One grid cell represents \(1\) unit. Which drawing shows the right half as the exact reflection of the left half?
Figure for problem 550664

Hints

- Reflected points stay at the same height across a vertical fold line. - Count how far corresponding vertices are from the dashed line. - Every corresponding pair must match, not just the top and bottom points.

Solution

1. In a), each right-side vertex is directly across the fold line from a left-side vertex at the same height and the same distance, so the halves are reflections. 2. In b), the upper right vertex is shifted upward, so the halves do not match. 3. In c), the middle right vertex is too close to the fold line, so the distances do not match. Therefore a) is the exact reflection.

Answer

a)
5506654
The dashed horizontal line is the fold line. One grid cell represents \(1\) unit. Which drawing shows the lower half as the exact reflection of the upper half?
Figure for problem 550665

Hints

- Across a horizontal fold, matching points have the same left-right position. - Compare each point's distance above or below the dashed line. - One mismatched vertex is enough to break symmetry.

Solution

1. Across a horizontal fold, reflected points stay directly above or below one another and keep the same distance from the fold line. 2. Drawing a) satisfies this for every vertex. 3. Drawing b) has one lower vertex too far from the fold, and drawing c) shifts one lower vertex sideways. Therefore a) is the exact reflection.

Answer

a)
5506664
The dashed vertical line is a fold line. One grid cell represents \(1\) unit. Which pair of labeled points are reflections of each other across the fold line?
Figure for problem 550666

Hints

- Reflections across a vertical line stay at the same height. - Count grid cells from each point to the dashed line. - Matching points must be equally far from the fold on opposite sides.

Solution

1. Points \(A\) and \(B\) are at the same height and each is \(3\) units from the fold line, on opposite sides. 2. Points \(C\) and \(D\) are at the same height, but their distances from the fold line are \(2\) units and \(1\) unit. 3. Points \(E\) and \(F\) are equally far from the fold line, but they are at different heights. Therefore \(A\) and \(B\) are reflections.

Answer

\(A\) and \(B\)
5506674
How many lines of symmetry does the concave figure on the geoboard have?
Figure for problem 550667

Hints

- Test vertical and horizontal folds first. - Then check whether either diagonal sends every corner to a matching corner. - Concave corners must match concave corners after a fold.

Solution

1. A vertical fold through the center matches the left and right halves. 2. A horizontal fold through the center matches the top and bottom halves. 3. A diagonal fold does not match the inward and outward corners. Therefore the figure has exactly \(2\) lines of symmetry.

Answer

\(2\)
5506684
Figure a) is a kite and figure b) is a non-square rhombus. How many lines of symmetry does each figure have, and which has more?
Figure for problem 550668

Hints

- Imagine folds through opposite vertices. - Test both diagonals of each figure. - Count only folds that make the entire outline match.

Solution

1. The kite in a) has one line of symmetry: the vertical line through its top and bottom vertices. 2. The rhombus in b) has two lines of symmetry: its two diagonals. 3. Therefore the rhombus has one more line of symmetry than the kite.

Answer

a) \(1\) line b) \(2\) lines The rhombus has more.
5506694
The dashed vertical line is a line of symmetry. Point \(P\) is shown on the left. Which labeled point is the reflection of \(P\)? One grid cell represents \(1\) unit.
Figure for problem 550669

Hints

- Keep the reflected point at the same height. - Count the grid cells from \(P\) to the dashed line. - Move the same number of cells to the other side.

Solution

1. Point \(P\) is \(2\) grid units left of the fold line. 2. Its reflection must be at the same height and \(2\) grid units to the right of the fold line. 3. Point \(R\) is in that position.

Answer

\(R\)
5506714
Which figure has exactly one line of symmetry?
Figure for problem 550671

Hints

- Test vertical, horizontal, and diagonal folds for each figure. - The word exactly rules out figures with more than one valid fold. - Count only folds that make every edge match.

Solution

1. Figure a), an isosceles trapezoid, has exactly one vertical line of symmetry. 2. Figure b), a non-square rectangle, has two lines of symmetry. 3. Figure c), a scalene triangle, has no line of symmetry. 4. Figure d), a square, has four lines of symmetry. Therefore a) is the only figure with exactly one line of symmetry.

Answer

a)
5190554
Determine whether each statement about line symmetry is true or false. Correct each false statement. a) Every rectangle has exactly four lines of symmetry. b) Every square has exactly four lines of symmetry. c) Every trapezoid has a line of symmetry.

Hints

- Imagine folding each kind of quadrilateral along possible mirror lines. - Compare the horizontal, vertical, and diagonal folds that work for a square and a non-square rectangle. - For a statement about every trapezoid, think about whether a lopsided trapezoid can match across any fold.

Solution

1. Statement a) is false. A rectangle that is not a square has exactly two lines of symmetry. A square has four. 2. Statement b) is true. A square has four lines of symmetry. 3. Statement c) is false. A trapezoid does not have to have a line of symmetry; a trapezoid with unequal nonparallel sides can have none.

Answer

a) False. A non-square rectangle has exactly two lines of symmetry; a square has four. b) True c) False. A trapezoid does not have to have a line of symmetry.
5372224
Examine figures a) through d). How many lines of symmetry does each figure have? A line of symmetry is a line along which you can fold a figure so that the two halves match exactly.
Figure for problem 537222

Hints

- Imagine folding each figure so that its edges match exactly. - A line of symmetry divides a figure into mirror-image halves. - Check lines through vertices and lines through side midpoints. - For regular polygons, look for repeated symmetry around the center.

Solution

1. Figure a) is a rectangle. It has \(2\) lines of symmetry: one horizontal and one vertical. 2. Figure b) is an equilateral triangle. It has \(3\) lines of symmetry, each passing through a vertex and the midpoint of the opposite side. 3. Figure c) is an isosceles trapezoid. It has \(1\) vertical line of symmetry. 4. Figure d) is a regular hexagon. It has \(6\) lines of symmetry: \(3\) through pairs of opposite vertices and \(3\) through midpoints of opposite sides.

Answer

a) \(2\) lines of symmetry b) \(3\) lines of symmetry c) \(1\) line of symmetry d) \(6\) lines of symmetry
5506704
Maya says, “A diagonal of any rectangle is a line of symmetry because it connects opposite corners.” Explain why Maya's statement is false for a non-square rectangle.

Hints

- Connecting two vertices is not enough to make a symmetry line. - Think about which sides would land on each other after the fold. - Compare the side lengths that a diagonal fold would pair.

Solution

1. A line of symmetry must fold the entire rectangle onto itself. 2. Folding a non-square rectangle along a diagonal would try to match a long side with a short side. 3. Those sides have different lengths, so the halves do not match. Therefore a diagonal is not a line of symmetry for a non-square rectangle.

Answer

Maya is incorrect. A diagonal fold in a non-square rectangle would match a long side with a short side, so the two halves do not coincide.
5506724
A designer needs a tile outline with a vertical line of symmetry and a horizontal line of symmetry, but no diagonal line of symmetry. Which outline should the designer choose?
Figure for problem 550672

Hints

- Check all three requirements, including the condition that diagonal symmetry must be absent. - A square and a non-square rectangle do not have the same symmetry count. - Test the kite's horizontal fold as well as its vertical fold.

Solution

1. Outline a), a non-square rectangle, has vertical and horizontal symmetry but no diagonal symmetry. 2. Outline b), a square, also has diagonal symmetry, so it does not meet the final condition. 3. Outline c), a kite, has only vertical symmetry. Therefore a) meets all three requirements.

Answer

a)
5506734
A vertical fold line is a line of symmetry for a paper design. Point \(A\) is \(3\,\text{cm}\) to the left of the fold. Point \(B\) is \(5\,\text{cm}\) to the left of the fold, and its height is \(2\,\text{cm}\) greater than the height of \(A\). Describe where the reflected points \(A'\) and \(B'\) must be.

Hints

- A reflected point is the same perpendicular distance from the fold line on the opposite side. - A vertical fold changes left/right position but not height. - Track \(A\) and \(B\) separately before comparing their reflected positions.

Solution

1. Reflection keeps the perpendicular distance to the fold line, but moves the point to the opposite side. So \(A'\) is \(3\,\text{cm}\) to the right of the fold. 2. Likewise, \(B'\) is \(5\,\text{cm}\) to the right of the fold. 3. Reflection across a vertical line keeps vertical positions unchanged, so \(B'\) is still \(2\,\text{cm}\) higher than \(A'\).

Answer

\(A'\) is \(3\,\text{cm}\) to the right of the fold. \(B'\) is \(5\,\text{cm}\) to the right of the fold and is \(2\,\text{cm}\) higher than \(A'\).
5506744
The same concave figure is shown with four proposed fold lines. Which proposed lines are actual lines of symmetry? Explain why the others fail.
Figure for problem 550674

Hints

- Check where both the inward corners and the outward points would land. - A fold must match every boundary feature, not just the center. - Test vertical, horizontal, and diagonal candidates independently.

Solution

1. In a), the vertical fold matches the left and right halves, so it is a line of symmetry. 2. In b), the horizontal fold matches the top and bottom halves, so it is a line of symmetry. 3. In c) and d), diagonal folds do not match the inward corners with inward corners and the outward points with outward points. Therefore only a) and b) are lines of symmetry.

Answer

a) and b)

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