Two pipes together can fill a tank in 12 hours. If first pipe can fill the tank 10 hours faster than the second, then how many hours will the second pipe take to fill the tank ?

Answer 1

the combined work rate is 1/12

1/x + 1/(x+10) = 1/12

12(x+10) + 12x = x(x+10)

12x + 120 + 12x = x^2 + 10x

24x + 120 = x^2 + 10x

0 = x^2 - 14x - 120

0 = ( x - 20 )( x + 6 )

x+6=0 results in negative measures

x=20

1/20 + 1/30 = 50/600 = 1/12

fast pipe takes 20 hours

slower pipe takes 30 hours