Answer :
Answer:
Option B is the answer.
Step-by-step explanation:
Given is that all 3 machine works at same rate or [tex]\frac{1}{x}[/tex]
We get; [tex]\frac{1}{x} +\frac{1}{x} +\frac{1}{x} =\frac{1}{36}[/tex]
=> [tex]\frac{3}{x} =\frac{1}{36}[/tex]
x = 108
Now given is that the fourth machine was used with same rate that is [tex]\frac{1}{x}[/tex]
Total rate for 4 machines = [tex]\frac{4}{x}[/tex]
= [tex]\frac{4}{108}[/tex]
= [tex]\frac{1}{27}[/tex]
This is the over all rate of four machines.
And we know that time = 1/Rate
So, time = 27 hours
Therefore, the fewer hours were [tex]36-27=9[/tex] hours
Option B is the answer.