WAEC 2011 Mathematics · Question 24
The height of a cylinder is equal to its radius. If the volume is 0.216 m. Calculate the radius.
Options
- A.0.46m
- B.0.60m
- C.0.87m
- D.1.80m
Answer: B. 0.60m
Explanation written with AI and checked against the answer key
Analyze the question: A cylinder has height h equal to its radius r. Its volume is 0.216π m³, and we need r. Concept: The volume of a cylinder is V = πr²h. Solution: Since h = r: V = πr²(r) = πr³ Set this equal to the given volume: πr³ = 0.216π Divide both sides by π: r³ = 0.216 Take the cube root. Since 0.216 = 216/1000 and 6³ = 216, 10³ = 1000: r = 6/10 = 0.6 m Check: 0.6³ = 0.6 × 0.6 × 0.6 = 0.36 × 0.6 = 0.216 ✓ Answer: The radius is 0.60 m, which is option B. Tip: When the height equals the radius, the volume formula collapses to V = πr³. Then just cancel π and take the cube root. Memorize common cubes (2³=8, 3³=27, 4³=64, 5³=125, 6³=216) so you can handle decimals like 0.216 quickly by thinking of 216/1000.AI can make mistakes. Report anything that looks wrong.
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