Question

Two taps A and B can fill a tank in 25 min and 40 min, respectively. Both the taps are opened together but after 10 min, tap A is turned off. What is the total time required to fill the tank?

• A. 22 min
• B. 24 min
• C. 18 min
• D. 14 min

Answer 1

The correct option is B 24 min

Given:

Time taken for tap A to fill the tank = 25 min

Consider a full tank of 100 units.

Water filled in the tank in one min = $\frac{100}{25}=4\text{units}$

Time taken for tap B to fill the tank = 40 min

Water filled in the tank in one min = $\frac{100}{40}=2.5\text{units}$

When both the taps are opened, water filled in one min = 4 + 2.5 = 6.5 units

In 10 minutes, amount of water filled = 6.5 × 10 = 65 units

It is given that after 10 minutes, tap A is closed.
So, only tap B is filling the remaining amount of water in the tank.

Remaining amount of water
= 100 units – 65 units = 35 units

∴ Time required to fill the remaining tank by tap B
$=\frac{\text{Remaining units}}{\text{Water filled in one min by tap B}}$

$=\frac{35}{2.5}$

$=14$

So, total time required to fill the tank completely is 10 + 14 = 24 minutes.