Question

15 pipes each having the same diameter, can fill a cistern in 12 minutes. How long will it take for 6 pipes, each with double the original diameter to fill the same cistern at the same speed of the flow

Answer 1

Solution:

15 pipes each having the same diameter=d, can fill a cistern in 12 minutes.

Time taken by 1 pipe having diameter=d, to fill the tank completely= 15 × 12= 180 minute

Time taken by 6 pipe to fill the tank completely having diameter  d= $\frac{180}{6}$=30 minute

If , in place of pipe having diameter d is replaced by pipe having diameter 2 d, the time required to fill the cistern will be less that is half of time required by 6 pipes to fill the tank.

So, Time taken by 6 pipes each with double the original diameter to fill the same cistern at the same speed of the flow= $\frac{30}{2}$=15 minutes