WAEC 2022 Mathematics · Question 35
Find the correct to two decimal places, the volume of a sphere whose radius is 3cm. [Take π = ]
Options
- A.72.57cm
- B.88.12cm
- C.10529cm
- D.113.14cm
Answer: D. 113.14cm
Explanation written with AI and checked against the answer key
Analyze the question: We need the volume of a sphere with radius 3 cm, using π = 22/7, correct to 2 decimal places. Concept: Volume of a sphere = (4/3)πr³ Solution: V = (4/3) × (22/7) × 3³ V = (4/3) × (22/7) × 27 The 3 and 27 simplify: 27 ÷ 3 = 9 V = 4 × (22/7) × 9 V = (4 × 22 × 9) / 7 V = 792 / 7 V = 113.142857... V ≈ 113.14 cm³ Checking the options: 113. Tip: Always cancel before multiplying. Since r³ = 27 and the formula has a 3 in the denominator, the cancellation gives a clean 9 and makes the arithmetic faster. Also remember that the sphere formula is (4/3)πr³, while the surface area is 4πr². Examiners often include wrong options that come from mixing up formulas or miscalculating the cube.AI can make mistakes. Report anything that looks wrong.
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