Question

a water tank has an inlet and an outlet . the inlet is capable of filling the tank in 20 min and the outlet is capable of emptying the tank in 40 min when the inlet was opened to fill the empty tank the person did not notice that the outlet was open . so both the inlet and outlet were open in how much time will the tank be just filled

Answer 1

This is ur ans hope it will help you in case of any doubt comment below

Answer 2

Assuming the whole tank as 1

Time taken by the inlet to fill the tank = 20 min.

∴ In 20 mins, the inlet fill = 1 whole part

∴In 1 min,  the inlet fills = 1/20 th part

Time taken by the outlet to empty 1 whole part = 40 min

∴ In 1 min, the outlet empties = 1/40 th part

Since, 1/20 > 1/40, the tank fills when the inlet and outlet are open.

Now, the inlet and outlet are opened together for 1 min.

they fill = 1/20 - 1/40 = 1/40 th part of the whole tank.

∴Time taken to fill the whole tank = 1/(1/40)

                                                         = 40 / 1

                                                         = 40 mins

ANS = 40 mins