Grade 4 · Math · Unit 11 of 12
Polygons & Perimeter
Sides, symmetry and perimeter
What your child practises
Telling regular polygons (all sides and angles equal) from irregular ones, finding lines of symmetry, and measuring perimeter around regular and irregular shapes.
Prince Edward Island Curriculum curriculum outcome: SS5 · lines of symmetry in 2-D shapes
How we explain it
Children can open this short lesson before they practise.
- Perimeter is the distance around a shape. Add all the sides.
- A regular polygon has all sides and angles equal.
- A line of symmetry splits a shape into matching halves.
Example: A rectangle is 17 m long and 11 m wide. What is its perimeter? Two lengths and two widths. 17 + 11 + 17 + 11 = 56. Answer: 56 m
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
How many lines of symmetry does this shape have?
- 12
- 6
- 5
- 7
6
Hint: A line of symmetry is a fold line where both halves match exactly. A regular polygon has as many lines of symmetry as sides. This regular hexagon has 6.
Question 2
Which letter has a line of symmetry?
- Q
- G
- V
V
Hint: Imagine folding the letter. V can fold down the middle so both halves match exactly.
Question 3
Each square is 1 cm on a side. What is the perimeter of this rectangle?
🟦🟦🟦🟦🟦🟦🟦🟦🟦🟦🟦🟦🟦🟦🟦🟦🟦🟦🟦🟦🟦🟦🟦🟦🟦🟦🟦🟦🟦🟦🟦🟦🟦🟦🟦🟦🟦🟦🟦🟦answer boxcm
26 cm
Hint: Count the squares along the top (8) and down one side (5). Opposite sides match, so add 8 + 5 + 8 + 5.
Question 4
A rectangle is 7 m long and 5 m wide. What is its perimeter?
answer boxm
24 m
Hint: A rectangle has two long sides and two short sides. Add all four: 7 + 5 + 7 + 5. Or add 7 + 5 and double it.
Question 5
Which polygon is regular?
- pentagon
- rectangle
- parallelogram
pentagon
Hint: A regular polygon has all sides equal and all angles equal. All 5 sides are the same length and all 5 angles are equal.
Question 6
An irregular pentagon has these side lengths. What is its perimeter?
Side Length (cm) A 12 B 4 C 5 D 10 E 9 answer boxcm
40 cm
Hint: Perimeter is the distance all the way around, so add every side: 12 + 4 + 5 + 10 + 9. Tip: add pairs that are easy first.