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WAEC Mathematics 2014 Question 23

Question 23

Mensuration of Solids

The area of a sector of a circle with diameter 12 cm is 66 cm2. If the sector is folded to form a cone, calculate the radius of the base of the cone. [Take π = 22/7]

  1. A.3.0 cm
  2. B.3.5 cm
  3. C.7.0 cm
  4. D.7.5 cm
Show the answer and explanation

Answer: B (3.5 cm)

Explanation

The sector's radius 6 cm becomes the slant height. The cone's curved area πrl = 66, so 22/7 × r × 6 = 66 and r = 3.5 cm.