A pipe can fill a tank in 20 min. due to a leak in the bottom it filled in 30 min. How much time will the leak take to empty the tank.

Tim taken to fill $\left(a\right)=20\min \to 1\min \to {\frac{1}{20}}^{th}part$

Due to leak age it has taken $30\min \to 1\min \to -{\frac{1}{30}}^{th}part$

let the leakage pipe empty the tank in x min

$\frac{1}{20}-\frac{1}{x}=\frac{1}{30}$

$\frac{1}{x}=\frac{1}{20}-\frac{1}{30}\to \frac{1}{x}=\frac{1}{60}$

x=60 min

=1 hour