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题库 / Prep2007E2-DS-156
Each of the numbers w, x, y, and z is equal to either 0 or 1. What is the value of w + x + y + z ?
(1) ~$\frac{w}{2}+\frac{x}{4}+\frac{y}{8}+\frac{z}{16}=\frac{11}{16}$~
(2) ~$\frac{w}{3}+\frac{x}{9}+\frac{y}{27}+\frac{z}{81}=\frac{31}{81}$~
Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient.
Statement (2) ALONE is sufficient, but statement (1) alone is not sufficient.
BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.
EACH statement ALONE is sufficient.
Statements (1) and (2) TOGETHER are NOT sufficient.
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四个数分别等于0或者1，把分母转换成一样的后得出等式，1、2选项都只有一种特定情况成立。
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