WAEC 2011 Mathematics · Question 5
The height of a cylinder is equal to its radius. If the volume is 0.216 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: 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: r = ∛0.216 = ∛(216/1000) = 6/10 = 0.6 m Check: 0.6³ = 0.6 × 0.6 × 0.6 = 0.36 × 0.6 = 0.216 ✓ The radius is 0.60 m, which is option B. Tip: When a question gives a volume as a decimal like 0.216, 0.027, or 0.125, think of perfect cubes: 216 = 6³, 27 = 3³, 125 = 5³. Convert the decimal to a fraction over 1000 and take the cube root of the top and bottom separately. Also, always cancel π early when it appears on both sides.AI can make mistakes. Report anything that looks wrong.
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