GRE数学(Barron模考)每日一题 第43期
日期:2014-11-10 10:52(单词翻译:单击)
GRE数学试题
From the set of 6 letter A,B,C,D,E,and F,there are 20 different 3-letter subsets that could be selected.
参考答案
10^3 = 1000 - 74 = 926
10^4 = 10000-74 = 9926
10^5 = 100000 - 74 = 99926
规律：50-2=48个9和26
所以： 48*9+2+6 = 432 + 2 + 6 = 440 C
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