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.
N= 824x, where x is a positive integer.
选项
答案B
解析 Note that the units digit of a product of positive integers is equal to the units digit of the product of the units digits of those integers. In particular, since 824x is a product of x integers, each of which is 824, it follows that the units digit of 824x is equal to the units digit of 4x. Also, the units digit of 4x is equal to the units digit of the product(4)(units digit of 4x-1).
The following table shows the units digit of 4x for some values of x, beginning with x = 2.

From the table, you can see that the units digit of 4x alternates, and will continue to alternate, between 4 and 6. Therefore, Quantity A, the number of possible values of the units digit of 824x, is 2. Since Quantity B is 4, the correct answer is Choice B.
This explanation uses the following strategies.
Strategy 7: Find a Pattern
Strategy 12: Adapt Solutions to Related Problems
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本试题收录于： GRE QUANTITATIVE题库GRE分类
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