A tank normally filled in 8 hours takes 2 hours longer owing to a leak. If the tank is full the leak shall empty in _________ hours?
The Usual Method
It takes 8 hours for the tank to be filled, so of the tank will be filled in 1 hour.
Owing to the leak, the tank is filled in 8 + 2 = 10 hours, so of the tank will be filled in 1 hour.
Let the leak empty the tank in ‘x’ hours, so of the tank will be emptied in 1 hour.
Estimated Time to arrive at the answer = 45 seconds.
Since tank is filled in 1 hour by the inlet working alone and of the tank is filled in 1 hour by keeping both the inlet and the leak open, the time needed for the outlet to empty the tank should be both a multiple of 8 and 10. (Note: and ) The only option satisfying this criteria is option ‘4’.
Estimated Time to arrive at the answer = 10 seconds.