Question

A closed conical vessel is filled with water fully and is placed with its vertex down. The water is flow out at a constant speed. After 21 minutes, it was found that the height of the water column is half of the original height. How much more time in minutes does it require to empty the vessel ?
A. 21
B. 14
C. 7
D. 3

Answer 1

Correct Answer - D
Rate of outflow of water `rArr (pi r^(2)h-pi((r)/(2))^(2)(h)/(2))` liters in 21 minutes i.e., `(7 pi r^(2)h)/(8)L` in 21 minutes.
Hence `(pi r^(2)h)/(8)L` in 3 min.