To find out the time taken to get filled completely, we need to know the net rate at which the tank gets filled (i.e. the rate at which the inlet fills the tank - the rate at which the lean drains the tank)
Statement 1(1) Total capacity of water the tank can hold is 120 gallons.
We do not have any information on the rate at which the inlet pipe and the leak works. Hence we can eliminate this option.
Eliminate A and D.
Statement 2(2) Inlet pipe can completely fill the empty tank in 10 hours if there is no leak in the tank, and also the leak at the bottom of the tank can completely empty the filled tank in 15 hours if there is no water pumped into the tank.
We are given the rate , so lets see how can we use this option to our advantage.
Inlet pipe can completely fill the empty tank in 10 hours if there is no leak in the tank - So in one hour the inlet pipe can fill \(\frac{1}{10}\) th of the tank (provided there is no leak)
the leak at the bottom of the tank can completely empty the filled tank in 15 hours if there is no water pumped into the tank - So in one hour the leak can drain \(\frac{1}{15}\)th of the tank (provided there is no water pumped into the tank).
Now if both are at play, in hour (\(\frac{1}{10} - \frac{1}{15}\)) of the tank gets full
\(\frac{3-2}{30}\) = \(\frac{1}{30}\) of the tank gets filled each hour.
So for the complete tank to get filled completely it will take 30 hours.
This information is sufficient.
Option B