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 Radius 3 cm. Area to 1 dp, in cm2? (π ≈ 3.142)
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3.142 × 9 = 28.3 cm2.
2 Radius 10 cm. Area to 1 dp, in cm2? (π ≈ 3.142)
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3.142 × 100 = 314.2 cm2.
3 A circle has diameter 8 cm. What is its radius, in cm?
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r = 8 ÷ 2 = 4 cm.
Level 2 · Core
4 A circle has diameter 14 cm. Area to 1 dp, in cm2? (π ≈ 3.142)
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r = 7 → 3.142 × 49 = 153.9 cm2.
5 Find the area of a quarter circle with radius 8 cm, to 1 dp, in cm2. (π ≈ 3.142)
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¼ × 3.142 × 64 = 50.3 cm2.
6 A circle has radius 6 cm. Give its area in terms of π. (in terms of π)
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62 = 36, so A = 36π cm2.
Level 3 · Challenge
7 A ring has outer radius 9 cm and inner radius 4 cm. Area to 1 dp, in cm2? (π ≈ 3.142)
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π(81) − π(16) = 254.5 − 50.3 = 204.2 cm2.
8 A circle has area 200 cm2. Find its radius to 1 dp, in cm. (π ≈ 3.142)
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r2 = 200 ÷ 3.142 = 63.7, so r = 8.0 cm.
9 A 20 cm pizza costs $10 and a 40 cm pizza costs $30. Which is better value — the 20 cm or the 40 cm?
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20 cm: area ≈ 314 cm2 for $10 → 31 cm2/$. 40 cm: area ≈ 1257 cm2 for $30 → 42 cm2/$. The 40 cm wins.