The diagram below shows a cone with the dimensions of its frustrum indicated. Calculate the...

MATHEMATICS
WAEC 1995

The diagram below shows a cone with the dimensions of its frustrum indicated. Calculate the height of the cone.

  • A. 12cm
  • B. 15cm
  • C. 18cm
  • D. 24cm

Correct Answer: D. 24cm

Explanation

Considering the smaller and larger triangle, these two are similar triangles. Hence,

If the height of the smaller triangle = h,

\(\therefore \frac{h}{6} = \frac{h + 12}{12}\)

\(12h = 6h + 72 \implies 6h = 72\)

\(h = 12 cm\)

\(\therefore\) The height of the cone = 12 + 12 = 24 cm



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