Management Aptitude Test 2017 Paper

(c) Waste pipe emptying the tank in 5 hours.
Tap 1 fills $\frac{1}{5}$th part in 1 hour.
Tap 2 fills $\frac{1}{10}$th part of tank in 1 hour.
Let, tap 3 fill the tank in x hours.
Then, tank filled by Tap 1, 2 and 3 in 1 hour.
⇒ $\frac{1}{5}+\frac{1}{10}+\frac{1}{\mathit{x}}=\frac{1}{10}$
⇒ $\frac{1}{\mathit{x}}=\frac{1}{10}-\left(\frac{1}{5}+\frac{1}{10}\right)$
⇒ $\frac{1}{\mathit{x}}=\frac{1}{10}-\frac{3}{10}$
⇒ $\frac{1}{\mathit{x}}=-\frac{2}{10}=-\frac{1}{5}$
⇒ x = - 5
(-ve sign show that tap 3 is emptying the tank in 5 hours.)