Two pipes A and B can fill a tank in 2 and 6 minutes respectively. If both the pipes are used together, then how long will it take to fill the tank?
3 min
2.5 min
2 min
1.5 min
Explanation:
Part filled by first pipe in $1$ minute $=\dfrac{1}{2}$
Part filled by second pipe in $1$ minute $=\dfrac{1}{6}$
Net part filled by pipe A and B in $1$ minute
$=\dfrac{1}{2}+\dfrac{1}{6}=\dfrac{2}{3}$
i.e, pipe A and B together can fill the tank in $\dfrac{3}{2}$ minutes $=1.5$ minutes.