A tank can be filled by two pipes A and B in 16 minutes and 24 minutes respectively. If both the pipes are opened together, after how much time B should be closed so that the tank is full in 10 minutes ?

9 minutes

The correct answer is Option (1) → 9 minutes

Work done by A and B in $x$ minutes + work done by A in $(10-x)$ minutes = 1

$⇒x(\frac{1}{16}+\frac{1}{24})+(10-x)×\frac{1}{16}=1$

$⇒2x+30=48$

$⇒x=9\text{ min}$