Question
1. ( (2) x=20 ) min and ( y=30 ) min ( begin{aligned} therefore text { Total taken time } &=frac{x y}{x+y}=frac{20 times 30}{20+30}=frac{20 times 30}{50} &=12 mathrm{min} end{aligned} )

1. Two pipes A and B can fill a tank in 20 min and 30 min respectively. If both pipes are opened together, the time taken to fill the tank is (1) 50 min (2) 12 min (3) 25 min (4) 15 min
Solution
