An electric pump fills a tank in 3 hours. Due to leakage in the tank, it took 3 hours 30 min to fill. In how much time will the leakage drain out all the water of the tank make it empty ?
Answer: D
We can get the answer by subtrating work done by leak in one hour by subtraction of filling for 1 hour without leak and with leak, as
Work done for 1 hour without leak = 1/3
Work done with leak =
3 1/2=7/2
Work done with leak in 1 hr = 2/7
Work done by leak in 1 hr = 1/3−2/7 = 1/21
So tank will be empty by the leak in 21 hours.