Question

A gardener uses pipes to water his garden from a tank. He uses 6 pipes to do it and it takes 1 hour 20 minutes to completely empty the tank. Now, if he uses only 5 pipes to water the garden, how long will it take to empty the tank?

• A. 1 hour 30 mins
• B. 1 hour 36 mins
• C. 1 hour 45 mins
• D. 1 hour 55 mins

Answer 1

The correct option is B 1 hour 36 mins

Let the time required be x.

If the number of pipes used to empty the tank is increased, then time required to empty it will decrease.

Hence, the number of pipes and the time required are inversely related.

No. of pipes	6	5
Time taken(min)	80	x

$\Rightarrow 6\times 80=5x$
$\Rightarrow x=\frac{480}{5}=96$ mins
$\Rightarrow x=$ 1 hour 36 mins