Question

one tap fills a bath tub in 12 minutes and another tap fills it in 15 minutes. The waste pipe can empty the bath tub in 10 minutes .In what time will the bath tub be filled if both the taps are turned on and if the waste pipe has been left open accidentally

Answer 1

Let the taps be A and B for the ones filling the bath tab and c for the ones emptying the bath tab.

Let the time they take to fill the tank and empty be a and b for the ones filling and c for the one emptying.

The formula is :

1/b + 1/a - 1/c = 1/x

x = time taken to fill the tank when all the tanks are opened .

Doing the substitution we have :

1/15 + 1/12 - 1/10 = 1/20

The taps take 20 minute to fill the tank when all are opened.