RRB Group-D Model Paper 12 with answers for online practice

Let the number of hours which leak takes to empty a cistern be t.
A cistern which could be filled in 9 hours takes one hour more to be filled owing to a leak in its bottom i.e. with the leak it is filled in 10 hours
⇒ 1/9 – 1/t = 1/10
⇒ 1/t = 1/90
⇒ t = 90 hours