A pipe can fill a tank in 7 hours. Another pipe can empty the full tank in 21 hours. If both the pipes are opened simultaneously, then how much time (in hours) will it take to fill two-thirds of the tank?
A pipe can fill a tank in 7 hours. Another pipe can empty the full tank in 21 hours. If both the pipes are opened simultaneously, then how much time (in hours) will it take to fill two-thirds of the tank? एक पाइप एक टंकी को 7 घंटे में भर सकता है। दूसरा पाइप भरी […]