There are two inlet pipe in the tank which can fill the tank in 15 and 20 hours respectively. There are two leaks in the tank too, having same efficiency one at the bottom of the tank and other at 3/4th height of the tank. Find the time in which the tank will get filled, if the bottom leak can empty the tank in 30 hours.?

Option 2 : 14 hours

Suppose the capacity of tank = 60 units (LCM of 15, 20 & 30)

∴ Efficiency of inlet pipe 1 = 60/15 = 4

Efficiency of inlet pipe 2 = 60/20 = 3

Efficiency of each leak = 60/30 = 2

Since one leak is at the bottom of the tank and other at 3/4^th height of the tank;

∴ 2^nd leak will not work unit the tank is 3/4^th full.

∴ Time in which the tank will get 3/4^th full (45 units) = 45/(4 + 3 – 2) = 9 hours

Now remaining 15 units is to be filled with both the leaks working:

∴ Time in which the remaining 15 units get filled = 15/(4 + 3 – 2 – 2) = 5 hours