Haryana Police Constable Model Paper 1

Given:
Time is taken by pipe to fill the tank = 12 hours
Time is taken by both pipe and leak to fill the tank = 20 hours
Formula used:
Time is taken = $\frac{\mathrm{Total}\mathrm{work}}{\mathrm{Efficiency}}$
Calculation:
Part of the tank filled by the pipe in 1 hour = $\frac{1}{12}$
Part of thetank filled by pipe and leak in 1 hour = $\frac{1}{20}$
Part of the tank empty by a leak in 1 hour = $\frac{1}{12}-\frac{1}{20}=\frac{1}{30}$
Total time is taken by the leak to empty full tank = 30 hours
∴ The time is taken by the leak to empty the full tank in 30 hours