几道数学问题求教

littlecorn · 发表于 2010-1-12 23:44:49

请好心人帮我解答以下问题

1. a first-grade teacher use ten flash cards, numbered 1 through 10, to teach her students to order numbers correctly. she has students choose four flash cards randomly, then arrange the cards in ascending order. one day, she removes the cards numbered 2 and 4 from the deck of flash cards. on that day, how many different correct arrangements of four randomly selected cards are possible?

选项A70 B210 C336 D840 E1680

2. if n is a positive integar and n²is divisible by72,then the largest positive integar that must divide n is

选项 A6 B12 C24 D36 E48

zhangfang923 · 发表于 2010-1-12 23:53:39

A,70 吧，就是C8,4 8中选4个，排列按照升序排列。
D,36, 整数和它们平方能被72整除，最大酒食36了

bajisitan · 发表于 2010-1-13 01:24:22

请好心人帮我解答以下问题

1. a first-grade teacher use ten flash cards, numbered 1 through 10, to teach her students to order numbers correctly. she has students choose four flash cards randomly, then arrange the cards in ascending order. one day, she removes the cards numbered 2 and 4 from the deck of flash cards. on that day, how many different correct arrangements of four randomly selected cards are possible?

选项A70 B210 C336 D840 E1680

2. if n is a positive integar and n²is divisible by72,then the largest positive integar that must divide n is

选项 A6 B12 C24 D36 E48

-- by 会员 littlecorn (2010/1/12 23:44:49)

第二题我觉得是48，n^2是72的倍数，72=36*2，说明n至少是6*2=12，那么能整除12的最大正整数是48。

如有不周之处，请指教

zhangfang923 · 发表于 2010-1-13 01:30:26

is divisible by 理解错了，应该是48

littlecorn · 发表于 2010-1-14 00:36:45

第二题答案是B，12，我就是不明白，请教大家看看，或者说答案错了，题目出自《陈向东的数学高分快速突破》

biantaishabi · 发表于 2010-1-14 07:04:34

72=2^3x3^2
能整除N^2, 所以n^2中至少有2^4x3^2
所以n中至少有2^2x3,所以是12

几道数学问题求教

所属分类: GMAT考试

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