三道题目求解 谢谢各位帮忙 二月一日北美考试

woshishizhan

If X^4+Y^4=100, then the greatest possible value of X is between
0-3
3-6
6-9
9-12
12-15
A company plans to assign identification numbers to its employees. Each number is to consist of four different digits from 0 to 9, inclusive, except that the first digit can't be 0. How many different identification numbers are possible?
3024
4536
5040
9000
10,000
A certain city with a population of 132000 is to be divided into 11 voting districts, and no district is to have a population that is more than 10 percent greater than the population of any other district, what is the minimum possible population that the least populated district could have?
10700
10900
10900
11000
11100

zhangyupeng120

楼主你好。第一题说求X最大值，极端情况可以把Y看做0.就是求X四次方等于100的最大情况。试数可以发现，4的4次方是16乘16一定是大于100的，3的四次方就是81，在一百以内，所以X最大情况就是3和4之间，也就是选项中的3到6.


第二题，关键在于每个digit要different，说千位数不能取0，所以总共10个数字，减去一个0，在剩下的9个数中取一个，百位数可以取0但是要减去千位数取过的数，所以也就是在所以10个数中减去千位取的数也就是9个取一个，同理百位数是8个取一个，个位数是7个取一个。所以最后答案是9*9*8*7=4536.


第三题，因为每个州的数目不能超过10%，所以最优情况是10个州市一样的，最后一个州最小，其余10个州市最后一个州的110%。所以列出方程X+10*1.1X=13200，计算X可以得出答案。