Question

Two large and 1 small pumps can fill a swimming pool in 4 hours. One large and 3 small pumps can also fill the same swimming pool in 4 hours. How many hours will it take 4 large and 4 small pumps to fill the swimming pool.(We assume that all large pumps are similar and all small pumps are also similar.)

Answer 1

We can see through simple math that each large pump fill the pool at a rate equal to two small pumps, so we find how many small pumps it takes to fill the pool in 4 hours (5). Then find the equivalent number of small pumps in the final situation (12). I don't know how to explain it past that. It takes 1.6 hours.