an inlet pipe can fill a large water tank in 3 hours. an outlet pipe can empty the same tank in 5 hours. given an empty tank, at 8pm, activate both pipes. what time on the clock will it be before the tank is completely filled?

Answer 1

In any given hour,
fraction of tank filled, x = 1/3-1/5 = 2/15
Time to fill = 1/x = 15/2 = 7.5 hours