4th Grade Lines of Symmetry Worksheet Answer Key (PDF)

4th grade lines of symmetry worksheet answers – Maths PDF

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This 4th grade lines of symmetry worksheet answers covers lines of symmetry (Common Core 4.G.A.3), with a free PDF to print.

Key takeaway: This answer key helps fourth grade students and parents check lines of symmetry and see why each count is right.

Topic: Lines of Symmetry (4th grade)
Content: Step-by-step answers to 20 worksheet problems
Standards: 4.G.A.3
Answers: Every step shown, with the method to review
Format: Free printable PDF, US Letter, black and white

This answer key helps fourth grade students and parents check lines of symmetry and see why each count is right. Also, each solution names the shape, describes each line, and explains why some lines do not work.

The key covers all 20 problems, including the grid drawing in problem 13 and the table in problem 14. Then, real world answers use full sentences. Also, if your count differs, fold a paper copy of the shape and test each line. Then, plan about 15 minutes to compare and fix your work.

Each answer explains the fold that makes the halves match and gives the number of lines in bold. Many answers show the shape with its dashed lines of symmetry. Use them to check your own drawings.

Grade 4 · Common Core State Standards: 4.G.A.3

4th grade lines of symmetry worksheet answers: worksheet problems 1 to 10

1 – Is it symmetric?

Fold along the dashed line. The left wings land exactly on the right wings.

Yes, it is line-symmetric.

2 – Square

A square folds in half up and down, across, and along each of the two diagonals.

A square.

4 lines

3 – Rectangle

It folds in half across and up and down. The diagonals do not make matching halves.

2 lines

4 – Equilateral triangle

Each line runs from a corner to the middle of the opposite side. There are 3 corners.

3 lines

5 – Isosceles triangle

Only the line from the top corner down to the middle of the base works.

An isosceles triangle.

1 line

6 – Slanted parallelogram

Try folding it up and down, across, or along a diagonal. In every case the halves do not match.

0 lines

7 – Vertical lines in letters

A, H, M, and T are cut into matching left and right halves by a vertical line. B has only a horizontal line, and F and S have none.

A, H, M, T

8 – Horizontal lines in letters

B, E, and H are cut into matching top and bottom halves. F, L, and S have no line.

B, E, H

9 – Letters with no lines

A has a vertical line, H has two lines, and T has a vertical line. F, L, and S have none.

F, L, S

Worksheet problem 10 and after

10 – Regular pentagon

One line from each of the 5 corners to the middle of the opposite side.

A regular pentagon.

5 lines

Worksheet problems 11 and up

11 – Regular hexagon

3 lines join opposite corners and 3 lines join the middles of opposite sides: \(3 + 3 = 6\).

6 lines

12 – Circle

Every line through the center folds the circle into two matching halves. You can draw as many such lines as you like.

Too many to count (infinitely many)

13 – Complete the shape

Each corner on the left has a matching corner the same distance from the dashed line on the right. Join them in the same order.

Grid with a dashed line of symmetry.

The right half mirrors the left half

14 – Sort the shapes

A rhombus folds along each diagonal: 2.
Also, a kite folds along one diagonal: 1.
A regular octagon has 8 sides: 8.
No fold matches the halves: 0.

2, 1, 8, 0

15 – Stop sign

A regular polygon has as many lines as sides. An octagon has 8 sides.

A stop sign.

8 lines

16 – Butterfly spots

The right wings have 4 spots too: \(4 + 4 = 8\).

Add the spot on the body: \(8 + 1 = 9\).

9 spots

17 – Road signs

Yield sign: 3. Stop sign: 8. School-crossing sign: 1.

\(3 + 8 + 1 = 12\).

12 lines

18 – Words with symmetry

TOT: T, O, and T each have a vertical line, and the letters read the same from the right, so it matches.

HAT: reflected it would read TAH, which is different.

TOT yes; HAT no

Worksheet problem 19 and after

19 – Flag stripes

Flag A: the top stripe matches the bottom stripe, so a horizontal line through the middle works. A vertical line also works because each stripe is one color. That is 2 lines.

Flag B: top and bottom are different colors, so only the vertical line works. That is 1 line.

Flag A has 2 lines; Flag B has 1 line (only A has a horizontal line)

20 – Folding a square

A square has 4 lines of symmetry: 2 diagonals and 2 lines through the middles of opposite sides.

Diagonal folds make 2 triangles each: 2 ways. Middle folds make 2 rectangles each: 2 ways.

Check: \(2 + 2 = 4\).

A square.

4 ways; 2 make triangles and 2 make rectangles

Key facts behind this 4th grade lines of symmetry worksheet answers

Key facts

A line of symmetry splits a figure into two matching halves.
Also, a square has 4 lines of symmetry, a rectangle has 2, and an equilateral triangle has 3.
A regular polygon with n sides has n lines of symmetry.
Then, some figures, like a slanted parallelogram, have no lines of symmetry.
Check by folding: the edges and corners must line up exactly.

Common mistakes with this 4th grade lines of symmetry worksheet answers

Students match the count but not the lines. Instead, check that every line you drew splits the shape into mirror halves.
Students skip the drawing in problem 13. Instead, the key describes where each point of the new half belongs.
Students ignore the reason for zero lines in problem 6. Also, the reason is that no fold makes the halves match.
Students forget the letters with both lines. Instead, h has both a vertical and a horizontal line. Slow down at that step and check it twice.

How to use these solutions

Fold a paper copy to check any answer that differs from the key. Then, a fold settles the question quickly.
Redo each missed problem by listing the lines in order: vertical, horizontal, then diagonal. Repeat this habit on every problem for the best results.
Parents can ask the child to explain why a rectangle has fewer lines than a square. Repeat this habit on every problem for the best results.

Download the 4th grade lines of symmetry worksheet answers as a PDF with the button below and keep it with your notes.

4th grade lines of symmetry worksheet answers: frequently asked questions

Why does the stop sign in problem 15 have 8 lines?

A stop sign is a regular octagon with 8 equal sides. Four lines pass through opposite corners, and four pass through the midpoints of opposite sides. Together, that makes 8 lines of symmetry. A quick check like this takes only a few seconds and prevents most errors.

How many spots does the butterfly in problem 16 have?

The left wings have 4 spots, and the right wings match with 4 more. Also, the body spot sits on the line, so it counts once. The total is 4 plus 4 plus 1, which is 9 spots.

Does the word TOT look the same in a mirror?

Yes. T and O each have a vertical line of symmetry, so the word reads the same when reflected. The mirror swaps the first and last letters, and both are T. A quick check like this takes only a few seconds and prevents most errors.

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