2018 · Q77
The curved surface area of a right circular cone is 1.76 m² and its base diameter is 140 cm. What is the height of the cone?
Elementary MathematicsMensuration
- A10 cm
- B10√2 cm
- C20√2 cm
- D10√15 cm
Explanation
Curved surface area πrl = 1.76 m² = 17600 cm² with r = 70 cm gives l = 17600/(70 × 22/7) = 80 cm. Height = √(l² − r²) = √(6400 − 4900) = √1500 = 10√15 cm, option (D).