Answer:
5 hours
Step-by-step explanation:
Given the function
[tex]f(t)=80000 -16000t[/tex]
where t is time in hours and f(t) is the amount of water in liter
To find the time needed to drained the entire pool we have to make f(t)=0 and solve the equation for t
[tex]0=80000-16000t\\-80000=-16000t\\t=\frac{-80000}{-16000}\\ t=5[/tex]
So the time needed is 5 hours