We know that 12 out of 30 employees said they work overtime on a regular basis. If we assume that this sample represents well all the employees, we can extend this proportion to all employees:
![12/ 30 = x / 200 \iff x = (12\cdot 200)/(30) = 80](https://img.qammunity.org/2020/formulas/mathematics/high-school/qnj9kbanasw1qvufa3m8h4tyh8nyasdqta.png)
So, if 12 out of 30 randomly selected employees said they work overtime on a regular basis, we assume that 80 out of all the 200 employees work overtime on a regular basis.
Note that this is a strong assumption: in the worst case, there are 12 employees working overtime, and we have been unlucky to pick them all in our sample.
Anyway, if our assumption is correct, knowing that 80 out of 200 employees work overtime on a regular basis leads to a percentage of
![(80)/(200)=(40)/(100)=40\%](https://img.qammunity.org/2020/formulas/mathematics/high-school/23ty4cp5wuj617n2q9tea83g4o6uurkyrh.png)