Scott Woodbury-Stewart

GMAT OFFICIAL GUIDE PS – The average (arithmetic mean) score on a test taken by 10 students was x. If the average score…

The average (arithmetic mean) score on a test taken by 10 students was x. If the average score…

Solution:

We are given that the average score on a test taken by 10 students was x and need to find the average score in terms of x if the average score for 5 of those students was 8.

Thus, the overall sum was 10x and the sum for the 5 students was (5)(8)= 40.

We need to determine the average of the 5 remaining students.

The sum for the 5 remaining students was 10x – 40, and thus the average is:

(10x – 40)/5 = 10x/5 – 40/5 = 2x – 8

Answer: A 

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