MathDB
Arithmetic progression

Source:

February 24, 2006
arithmetic sequence

Problem Statement

When the mean, median, and mode of the list 10,2,5,2,4,2,x10,2,5,2,4,2,x are arranged in increasing order, they form a non-constant arithmetic progression. What is the sum of all possible real values of xx? (A) 3(B) 6(C) 9(D) 17(E) 20\text{(A)}\ 3\qquad\text{(B)}\ 6 \qquad\text{(C)}\ 9 \qquad\text{(D)}\ 17\qquad\text{(E)}\ 20
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