请教GWD1里几道数学题目不懂

xwqw · 发表于 2011-8-17 14:55:23

4.If n is the product of the integers from1 to 20 inclusive, what is the greatest integer k for which 2k is a factor of n?
10
12
15
18
20

Q25:
A photographer will arrange 6 people of 6 different heights for photograph by placing them in two rows of three so that each person in the first row is standing in front of someone in the second row. The heights of the people within each row must increase from left to right, and each person in the second row must be taller than the person standing in front of him or her. How many such arrangements of the 6 people are possible?

5
6
9
24
36

Q32:
For a convention, a hotel charges a daily room rate of $120 for 1 person and x dollars for each additional person. What is the charge for each additional person?
(1)The daily cost per person for 4 people sharing the cost of a room equally is $45.
(2)The daily cost per person for 2 people sharing the cost of a room equally is $25 more than the corresponding cost for 4 people.

dingsj1990 · 发表于 2011-8-17 15:01:25

第一题是2的K次方

wyw1018 · 发表于 2011-8-17 15:31:17

第一题，从1乘到20，其中偶数有2，4，6，8，10，12，14，16，18，20分别有2^1,2^2,2^1,2^3,2^1,2^2,2^1,2^4,2^1,2^2的因子。将2的指数因子相加和为18。因此k最大值为18.
第二题，设1，2，3，4，5，6为从低至高的6个人，依题意，1只能在第一排最左边，6只能在第二排最右边。剩下2，3，4，5的排列选择。2只能在第一排1的右边或者第二排1的后边。当2在第一排1的右边时，可有3种排法：123/456，124/356，125/346；当2在第二排1的后边时，有2种排法：134/256，135/246.因此共5种排法。

wyw1018 · 发表于 2011-8-17 15:43:27

第三题：
按条件（1）4*45=120+3x-->x=20
按条件（2）(120+x)/2=25+(120+3x)/4-->x=20
因此任何一个条件都可求出x

xwqw · 发表于 2011-8-17 16:36:45

哦哦这样哦谢谢啦~~

请教GWD1里几道数学题目不懂

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