Work through the levels in order. Type your answer and press Check — open the worked solution if you get stuck. Answers like -6, 3/4 or 0.25 are typed exactly as shown.
Level 1 · Warm-up
1 Find the perimeter of a rectangle 9 cm by 5 cm. (cm)
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2(9 + 5) = 2 × 14 = 28 cm.
2 Find the perimeter of a square with side 6 cm. (cm)
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4 × 6 = 24 cm.
3 A triangle has sides 5 cm, 7 cm and 9 cm. Find its perimeter. (cm)
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5 + 7 + 9 = 21 cm.
Level 2 · Core
4 Find the perimeter of a regular hexagon with side 6 cm. (cm)
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6 sides × 6 cm = 36 cm.
5 Find the perimeter of a rectangle 11 cm by 4 cm. (cm)
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2(11 + 4) = 2 × 15 = 30 cm.
6 A regular pentagon has sides of 8 cm. Find its perimeter. (cm)
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5 × 8 = 40 cm.
Level 3 · Challenge
7 A rectangle 14 cm by 9 cm has a 4 cm by 3 cm rectangle cut out of one corner, leaving an L-shape. Find the perimeter of the L-shape. (cm)
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The cut swaps two edges for two equal ones, so the perimeter is still 2(14 + 9) = 46 cm.
8 A rectangle has a perimeter of 30 cm and a length of 9 cm. Find its width. (cm)
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30 = 2(9 + w) → 15 = 9 + w → w = 6 cm. Check: 2(9 + 6) = 30 ✓
9 A rectangle is 1.2 m by 40 cm. Find its perimeter in centimetres. (cm)
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1.2 m = 120 cm, so 2(120 + 40) = 320 cm (which is 3.2 m).