Grade 5 · Math · Unit 13 of 14
Symmetry
Mirror lines and turns
What your child practises
Lines of reflection symmetry, the order of rotational symmetry and how both work for regular polygons (a regular polygon with n sides has n lines of symmetry and rotational symmetry of order n).
Alberta Curriculum learning outcome: 5G1.1, 5G1.2 · reflection and rotational symmetry in 2D shapes and regular polygons
Sample questions
A taste of this unit. In the app, questions change every time and get easier or harder to match your child.
Question 1
What does it mean when a shape has a line of symmetry?
- Folding along the line makes the two halves match exactly
- The shape has no corners
- The shape has equal sides
- The shape is a regular polygon
Show answer
Folding along the line makes the two halves match exactly
Hint: Reflection symmetry means one half is the mirror image of the other half.
Question 2
A regular triangle turns around its centre. In one full turn, how many times does it look exactly the same as it started (counting the start)?
- 4
- 3
- 2
Show answer
3
Hint: This number is the order of rotational symmetry. A regular polygon has as many as it has sides.
Question 3
How many lines of symmetry does a rhombus that is not a square have?
- 4
- 2
- 1
- 0
Show answer
2
Hint: The two diagonals of a rhombus are its lines of symmetry.
Question 4
How many lines of symmetry does a regular polygon with 12 sides have?
- 12
- 10
- 11
Show answer
12
Hint: A regular polygon has the same number of lines of symmetry as sides.
Question 5
Which shape has rotational symmetry but no line of symmetry?
- a square
- an isosceles triangle
- a slanted parallelogram
- a rectangle
Show answer
a slanted parallelogram
Hint: A slanted parallelogram fits onto itself after a half turn, but folding never matches its halves.
Question 6
How many lines of symmetry does a regular square have?
- 2
- 6
- 4
Show answer
4
Hint: A regular polygon has one line of symmetry for each of its sides (or corners).