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WAEC Mathematics 2021 Question 27

Question 27

Mensuration of Solids

A solid brass cube is melted and recast as a solid cone of height h and base radius r. If the height of the cube is h, find r in terms of h.

  1. A.r = h
  2. B.r = √(3h/π)
  3. C.r = πh
  4. D.r = h√(3/π)
Show the answer and explanation

Answer: D (r = h√(3/π))

Explanation

Volumes are equal: h3 = ⅓πr2h, so r2 = 3h2/π and r = h√(3/π).