Question

The difference between the radii is 12 cm and slant height is given as 15 cm. Find the height of the frustum.

(a) 5.4 cm

(b) 1.2 cm

(c) 3 cm

(d) 9 cm

The question was posed to me during a job interview.

This intriguing question comes from Surface Area & Volumes in section Surface Area and Volumes of Mathematics – Class 10

Answer 1

The correct choice is (d) 9 cm

The explanation is: Given R – r = 12 cm and slant height = 15 cm

The slant height of a cone s^2 = h^2 + (R – r)^2

225 = h^2 + 144

h^2 = 225 – 144

h^2 = 81

h = 9 cm