2017 · Q73
The radii of the frustum of a right circular cone are in the ratio 2:1. What is the ratio of the volume of the frustum of the cone to that of the whole cone ?
Elementary MathematicsMensuration
- A1:8
- B1:4
- C3:4
- D7:8
Explanation
The frustum is the whole cone minus a similar top cone of half the linear dimensions (radii 2:1). Volume ratio of the small to the whole cone = (1/2)³ = 1/8, so frustum:whole = 7:8. Hence option (D) 7:8.