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标题: MATH 1 题，请帮忙 [打印本页]

作者: tantan 时间: 2003-1-4 20:14 标题: MATH 1 题，请帮忙

__________
__________
_________
_________
图就是四条横线如上所示，再画上三条竖线，象田的形状，左下是X点右上角是Y点。

TOM will from intersection X to intersection Y along a route that is confined to the square grid of four streets and three avennues shown in the map above. How many routes from X or Y can Tom take that have the minimum possible length.

answer ;6,8,10,14,16.选10

到是可以数出来，可是好象有一种方法是用排列组合来算的，请给讲一下，？

作者: kitten369 时间: 2003-1-5 01:36

Ok, there are five step to the destiny, three ||| and to__ __. so 5 elements to 排列 it is P(55), but ||| are same, then divied by P(33), two __ __ are same ,then divided by P(22),
finally the answer is P(55)/P(22)/P(33)=10.

Make sense?

作者: kitten369 时间: 2003-1-5 01:40

[此贴子已经被作者于2003-1-5 1:40:26编辑过]

作者: 卧室春竹 时间: 2003-1-5 19:10

呵呵
不如直接数数吧！

作者: kitten369 时间: 2003-1-6 01:12

if it is 5条横线,3条竖线, you still could get the answer by 直接数?

作者: 卧室春竹 时间: 2003-1-6 18:18

哦.

呵呵...我相信ets得智商...

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