If one pump can empty a flooded basement in 18 hours, and a second pump can empty the basement in 20 hours, how long will it take it to empty the basement when both pumps are uses?

It would take approximately 9.47 hours.

Step-by-step explanation:

Given :  One pump can empty a flooded basement in 18 hours, and a second pump can empty the basement in 20 hour.

Let 't' be the time both of them together to fill the tank.

Now , the total time taken to empty the basement when both pumps are uses :-

Hence, it would take approximately 9.47 hours.

both equations and proportions are better.