A cylindrical candle (radius 3 cm, height 10 cm) burns evenly and reduces 1 cm in height every 2 hours. In how many hours will 70% of the candle's volume be burned?
Show answer & explanation
Correct answer: B
Explanation
Radius r = 3 cm
Initial height = 10 cm
Height decreases by 1 cm every 2 hours
70% of the volume burns ⇒ 70% of the height burns
Height burnt = 70/100 × 10 = 7 cm
Time taken to burn 1 cm = 2 hours
Time taken to burn 7 cm = 7 × 2 = 14 hours