SAT Math Multiple Choice Practice Question 339: Answer and Explanation
9. How much greater is the average (arithmetic mean) of a, b, and 18 than the average of a, b, and 12?
Correct Answer: A
A The sum of a, b, and 18 is 6 greater than the sum of a, b, and 12. Since there are three terms in the group, it follows that the average of a, b, and 18 would be greater than the average of a, b, and 12.