Question

One pipe can fill a tank three times as fast as another pipe. If together the two pipes can fill the tank in $36$ minutes, then the slower pipe alone will be able to fill the tank in

• A. $81$ minutes
• B. $108$ minutes
• C. $144$ minutes
• D. $192$ minutes

Answer 1

The correct option is C $144$ minutes

Let the slower pipe alone fill the tank in $x$ minutes.
Then, the faster pipe will fill it in $\frac{x}{3}$ minutes.
$\therefore \frac{1}{x}+\frac{3}{x}=\frac{1}{36}$
$\Rightarrow \frac{4}{x}=\frac{1}{36}$
$\Rightarrow x=144$ min