If the average (arithmetic mean ) of x, y, z, 5 and 7 is 8, which of the following must be true? I. The median of the five num

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问题 If the average (arithmetic mean ) of x, y, z, 5 and 7 is 8, which of the following must be true?
I.   The median of the five numbers cannot be 5.
II.   At least one of x, y, and z is greater than 9.
III.   The range of the five numbers is 2 or more

选项 A、I only
B、II only
C、III only
D、I and III
E、II and III

答案E

解析 若x,y,z,5和7的算术平均值是8,下面哪一个一定正确?
  I.5个数字的中数不能是5。
  II.x,y和z中至少有一个大于9。
  III.5个数字的值域是2或更大。
解:本题的正确答案是(E)。I不对,因为5个数的中数完全可以是5。II一定正确,因为算术平均值为8,则x,y,z中至少有一个大于9。III一定正确,因为x,y,z中至少有1个大于9,那么range至少大于4,2 or more必然满足大于4。
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本试题收录于: GRE QUANTITATIVE题库GRE分类
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