题库搜索>问题求解PS-17738
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In the figure above, X and Y represent locations in a district of a certain city where the streets form a rectangular grid. In traveling only north or east along the streets from X to Y, how many different paths are possible?
分析A选项
分析B选项
分析C选项
分析D选项
分析E选项
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从X到Y一共要走8步，其中3步是往北走的，5步是往东走的。可以简化成一个简单的组合问题，确定8步中哪3步是往北走的，就能计算出一共有多少种选择。
265281drgas
为什么横固定了，竖就固定了？
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2022-12-15 00:45:05
555917etdd
2^8
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2022-11-01 14:12:53
311475pmvj
8个空位子，往北是三个，往东是5个，把三个北放在8个位子里，问有多少种放法
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2022-09-18 12:04:19
680461elv
共八步，五步向左，三步向上，且选定任意一个方向的路线后，另一个方向相应的路线自动确定，所以求C（8，3）或者C（8，5）都可以
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2022-08-12 12:17:07
灭绝人性
没有人质疑一下 这题的选择 每一步的往东 往北 其实是固定的 先要到1 才可以到2？ 那么就没办法套用C（8.5） 因为必须按照 1 .2.3的顺序选择
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2022-06-26 04:15:45
努力滚动的绿猪猪
如果不知道这条规则，可以查一下Mississippi rule。
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2022-03-12 15:45:00
Crystal8
一共走八步，其中三步向上，五步向右‼️我是知道这个原理的，但是之前搞不清这样就可以用C3 8排列表示，现在明白了：共八步，给这八步分别命名为ABCDEFGH，这八个字母中有3个是
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2021-12-09 14:58:26
304247yrdh
C83
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2021-07-07 15:05:24
186871ad
这个题其实就是5个向右和3个向上的排列有多少种方式
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2021-06-07 01:17:24
186871ad
这个题其实就是5个
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2021-06-07 01:16:28
carpe diem
C（8，5）*C（3，3）=56
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2019-11-23 22:53:32
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问题求解PS
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