Question

3 PUMPS WORKING 8 HOURS A DAY, CAN EMPTY A TANK IN 2 DAYS. HOW MANY HOURS A DAY MUST 4 PUMPS WORK TO EMPTY THE TANK IN 1 DAY?

Answer 1

The three pumps work 3*8*2=48 hrs in 2 days, so one pump can empty 1/48 of the tank in an hour.

4 pumps can empty 4/48 = 1/12 of the tank in one hour.

so, . . .

Answer 2

10