Question

I'm too tired to math. I would give more points, but people always spam when I do that. Pls help!

Working together, two pumps can drain a certain pool in 3 hours. If it takes the older pump 7 hours to drain the pool by itself, how long will it take the newer pump to drain the pool on its own?

Answer 1

In 1 hour, both the pumps can drain 1 : 3 = 1/3 of the pool

And in an hour, the older pump can drain 1 : 7 = 1/7 of the pool

So in 1 hour, the newer pump will drain 1/3 - 1/7 = 4/21 of the pool

It will take the newer pump 1 : 4/21 = 21/4 hours to drain the pool on its own.