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JAMB 1998 · UME · Q30

A cylindrical drum of diameter 56 cm contains 123.2 litres of oil when full. Find the height of the drum in centimetres. [π=227]\left[\pi = \frac{22}{7}\right]

Worked solution (try it first)
  1. Change litres to cm³: 1 litre is 1000 cm31000\text{ cm}^3, so the drum holds 123 200 cm3123\,200\text{ cm}^3.
  2. The radius is 56÷2=2856 \div 2 = 28 cm.
  3. Base area: 227×282=2464 cm2\frac{22}{7} \times 28^2 = 2464\text{ cm}^2.
  4. Volume = base area × height, so h=123 2002464=50h = \dfrac{123\,200}{2464} = 50 cm, option D.

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