A cistern is filled by a tap in 3 1/2 hours. Due to leak in the bottom of the cistern, it takes half an hour longer to fill the cistern. If…

28 hours

NA

Solution;

Given;

The tap alone can fill the cistern in 3 (1/2) hours.

When there is a leakage, the cistern gets filled in 4 hours.

If the tap takes 3 (1/2) hours to fill the cistern, then in 1 hour it can fill,

=> 2/7 part of the cistern

If both the tap and the leakage takes 4 hours to fill the cistern, then in 1 hour they can fill,

=> 1/4 part of the cistern

Therefore in 1 hour, the leakage alone can empty,

=> (2/7) - (1/4)

=> 1/28 part of the cistern

So, the leakage alone takes 28 hours to empty the cistern.

The correct option is D). 28 hours