Two pipes A and  B can fill the tank in 24 minutes and 36 minutes respectively. If both the pipes are opened together, then what is the time in which the tank will be filled completely?

$14\, min 24 sec $

The correct answer is option (1) :$14\, min 24 sec $

Part of the tank filled by pipe A in 1 min $=\frac{1}{24}$

Part of the tank filled by pipe B in 1 min $=\frac{1}{36}$

$=\frac{1}{24}+\frac{1}{36}$

$=\frac{3+2}{72}=\frac{5}{72}$

∴ time taken to fill the tank $=\frac{72}{5}min$

$=14\, min 24 sec $