2017 · Q74
From a solid cylinder whose height is 8 cm and of base radius 6 cm, a conical cavity of height 8 cm and of base radius 6 cm is formed by hollowing out. What is the inner surface area of the cavity ?
Elementary MathematicsMensuration
- A6π square cm
- B8π square cm
- C10π square cm
- D60π square cm
Explanation
Only the cone's lateral surface is exposed: πrl with slant height l = √(8²+6²) = 10 cm. Inner surface area = π×6×10 = 60π cm². Hence option (D) 60π square cm.