WAEC 2012 Mathematics · Question 20
The curved surface area of a cylindrical tin is 704cm2. If the radius of its base is 8cm, find the height. [Take ]`
Options
- A.14cm
- B.9cm
- C.8cm
- D.7cm
Answer: A. 14cm
Explanation written with AI and checked against the answer key
Analyze the question: We're given the curved surface area (CSA) of a cylinder and its radius, and we need to find the height. Concept: The curved surface area of a cylinder is CSA = 2πrh Solution: Substitute the values: 704 = 2 × (22/7) × 8 × h Simplify the right side: 2 × 22 × 8 = 352, so 704 = (352/7) × h Make h the subject: h = (704 × 7) / 352 Since 704 ÷ 352 = 2: h = 2 × 7 = 14 cm Check: 2 × (22/7) × 8 × 14 = 2 × 22 × 8 × 2 = 704 ✓ Tip: When π = 22/7 is given, look for a factor of 7 to cancel. Here the answer had to be a multiple of 7, so only 14 cm or 7 cm were plausible, which helps you eliminate options quickly. Also remember to use CSA = 2πrh (not the total surface area, which adds 2πr²).AI can make mistakes. Report anything that looks wrong.
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