2. 外语
  3. Compare Quantity A and Quantity B, using additional information centered above the two quantities if such information is given,

Compare Quantity A and Quantity B, using additional information centered above the two quantities if such information is given,

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问题 Compare Quantity A and Quantity B, using additional information centered above the two quantities if such information is given, and select one of the following four answer choices:
(A)Quantity A is greater.
(B)Quantity B is greater.
(C)The two quantities are equal.
(D)The relationship cannot be determined from the information given.
A symbol that appears more than once in a question has the same meaning throughout the question.
List X: 2, 5,s, t
List Y: 2, 5, t
The average(arithmetic mean)of the numbers in list X is equal to the average of the numbers in list Y.
Quantity A   Quantity B
s            0
选项
答案D
解析 Since you are given that the average of the 4 numbers in list X is equal to the average of the 3 numbers in list 7, it follows that. To make it easier to compare Quantity A and Quantity B, you can simplify this equation as follows.

3(7 + s + t)= 4(7 + t)
21 + 3s + 3t = 28+4t
3s = 7 + t
From the equation 3s = 7 + t, if t = -7, then s = 0, but if t = 0, then s > 0. In one case, the quantities are equal, and in the other case, Quantity A is greater. Therefore the correct answer is Choice D.
This explanation uses the following strategies.
Strategy 1: Translate from Words to an Arithmetic or Algebraic Representation
Strategy 10: Trial and Error
Strategy 13: Determine Whether a Conclusion Follows from the Information Given
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本试题收录于： GRE QUANTITATIVE题库GRE分类
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