Question

water tank has an inlet and outlet .The inlet is capable of filling the tank in 20 ninutes and the outlet is capable of emptying the tank in 40 minutes when the inlet was opened to fill the empty tank the erson did not notice that the outlet was opened so both the inlet and the outlet where opened in how much time will the tank be just filled? ​

Answer 1

Inlet of tank = 20min

Work done by the inlet in 1 minutes=1/20

Outlet of tank = 40min

Work done by the outlet in 1 minutes = -1/40

So , work done by both at the same time= 1/20-1/40

=1/40

Now, time taken by both the systems open to fill the tank=40min

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.