A solid brass cube is melted and recast as a solid cone of height h...

MATHEMATICS
WAEC 2021

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.

  • A. r = h
  • B. r = √\(\frac{3h^2}{π}\)
  • C. r = πh
  • D. r = h √\(\frac{3}{h}\)

Correct Answer: B. r = √\(\frac{3h^2}{π}\)

Explanation

Volume of cube = H. H. H. = H\(^3\)

the volume of a cone is,V=\(\frac{1}{3}\)πr\(^2\)h.

Volume of cube = the volume of a cone

H\(^3\) =\(\frac{1}{3}\)πr\(^2\)h.

\(\frac{3{H}^3}{πh}\) =r\(^2\)

√\(\frac{3{H}^3}{πh}\) = r

h √\(\frac{3H^2}{π}\) = r



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