Answer: 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 :-
[tex]\dfrac{1}{t}=\dfrac{1}{18}+\dfrac{1}{20}\\\\\Rightarrow\ \dfrac{1}{t}=\dfrac{10+9}{180}\\\\\Rightarrow\ t=\dfrac{180}{19}\approx9.47[/tex]
Hence, it would take approximately 9.47 hours.
