问一道JJ里的题目 没有思路

yijijuechen

This is my analysis:

A: the average of X.
B:the average of Y.

Z: the average of Z.

a: the medium of X.

b: the medium of Y.

z: the medium of Z.

according to (1): we get a>z>b

according to (2): 5A+7B=12Z,we get A>Z>B

But we do not know if B>a, or if A>b.

so we can not get a solution. the correct selection is (E)

But if (1) is changed to a<b, and (2) remain unchanged, we get:

a<z<b,   A>Z>B, and B>b, so the outcome is Z>z.

If (2) is changed to A<B, and (1) remain unchanged. We get:

a>z>b, A<Z<B, and A>a, so the outcome is Z>z