NIACL Model Paper 8 with solutions for free online practice

(1) Part of tank filled by thepipe in 1 hour = $\frac{1}{10}$
Due to leak the pipe has to work extra 2 hours to fill the tank.
∴Part of tank filled by thepipe in 2 hours = $\frac{2}{10}=\frac{1}{5}$
Now $\frac{1}{5}$ th of the tank is emptied by the leak in 12 hours.
∴ The completely filled tank will get emptied in $12\times 5=60$ hours.
Aliter : Using direct formula,
Required time $=\frac{10\times 12}{12-10}$
= 60 hours
Aliter : $\frac{1}{10}-\frac{1}{\mathit{t}}=\frac{1}{12}$
⇒ $\frac{1}{\mathit{t}}=\frac{1}{10}-\frac{1}{12}$
= $\frac{6-5}{60}=\frac{1}{60}$
∴t = 60 hours