Arithmetics --leaking tank

There is a leak in the tank. Because of the leak, the tank which usually is filled in 3 hours, now takes 3.5 hours to be filled. The leak alone will empty the filled tank in ......................... hours.









Answer

Let "x" ltrs/hr be the filling rate of tank.

Under normal situation volume of tank = 3x ltrs

since the tank has a leak, the volume of water fed to tank to make it full is 3.5x  ltrs.

So, excess volume of water lost because of leakage = 3.5x - 3x = 0.5x ltrs

Time taken to loose 0.5x ltrs of water = 3.5 hrs
.
So, time it will take to loose 3x amount of water = (3x/0.5x) x 3.5 = 21 hours