two pump can individual fill the tank in 10 hours and 12 hours respectively while a third pump empites the full tank in 20 hours.If all the three pump are run simultaneously,in how munch time will be the tank be filled?

Answer 1

1/x = 1/10 + 1/12 - 1/20
x = 15/2

Answer 2

12/120 + 10/120 - 6/120

16/120 = 1/x

120/16 = x

15/2 =x