Question

A new type of pump can drain a certain pool in

8
hours. An older pump can drain the pool in
12
hours. How long will it take both pumps working together to drain the pool?

Answer 1

Rate = 1/time
New pump pumps at a rate of 1/8 pool per hour
Old pump at 1/12 pool per hour

Working together you ADD the rates
----> 1/8 + 1/12 = 3/24 + 2/24 = 5/24

That means, Time = 24/5 hours = 4.8 hours

Answer 2

4 to 6 hours add me im bored