Question

A water tank has two inlets & one outlet. Inlet 1 can fill the tank alone in 40 minutes & inlet 2 can fill the tank in 20 minutes. The outlet can empty tank in 30 minutes. If the tank is to be filled while both the inlet & outlet are open, how long will it take for tank to fill?

Answer 1

Answer:

120 minutes 1/30 - 1/40+1/20

Answer 2

inlet=20min=1/20 (A let)

outlet=40min=1/40 (B let)

hence, the work done by a&b

=a+b=1/20+(-1/40)=1/40

hence tank will get filled in 40 minutes.