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

3 pumps, working 8 hours a day, can empty a tank in 2 days.
let 4 pumps, working x hours a day, can empty a tank in 1 days.

So 3*8*2 = 4*x*1
⇒ 4x = 48
⇒x = 48/4 = 12 hours a day.

They must work 12 hours a day.