Five full-time employees and 6 interns work 12 hours a day and finish a task in 20 days. 8 full-time employees and 18 interns work 10 hours a day and finish the same task in 12 days. How many are working hours per day required if 5 full-time employees and 6 interns work for 30 days to finish the same amount of work? We may assume that changing number of people in a group does not change productivity.

**(A)** 8 hours a day

**(B)** 7 hours a day

**(C)** 6 hours a day

**(D)** 5 hours a day

**Answer:** **(A)** **Explanation:** (5 full time + 6 interns) * 12 * 20 = (8 full time + 18 interns) * 10 * 12

(5 full time + 6 interns) * 2 = (8 full time + 18 interns)

2 full time = 6 interns

1 full time = 3 interns.

Now (8 full time + 18 interns) * 10 * 12 = (5 full time + 6 interns) * x * 30

42 interns * 12 * 10 = 21 interns * x * 30

X = 8 hours a day.

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