题库搜索>问题求解PS-17738
建议使用官方纸质指南,查看对照完整题目
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
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?
555917etdd
2^8
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
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
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
努力滚动的绿猪猪
如果不知道这条规则,可以查一下Mississippi rule。
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
304247yrdh
C83
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
186871ad
这个题其实就是5个
carpe diem
C(8,5)*C(3,3)=56
科目:
问题求解PS
来源:
难题300
2m4s
平均耗时
60.2%
平均正确率
该题由网友LyyCy9P提供
点击上传问题求解PS -18031
1-According to a recent theory, Archean-age gold-quartz vein systems were formed more than two...
问题求解PS -18029
吃撒程度
问题求解PS -18027
Let S be the set of all positive integers having at most 4 digits and such that each of the digits is 0 or 1 What is the greatest prime factor of the sum of all the numbers in S?
问题求解PS -17760
The addition problem above shows four of the 24 different integers that can be formed by using each of the digits 1, 2, 3, and 4 exactly once in each integer. What is the sum of these 24 integers?
问题求解PS -17738
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?
问题求解PS -18031
1-According to a recent theory, Archean-age gold-quartz vein systems were formed more than two...
问题求解PS -18029
吃撒程度
问题求解PS -18027
Let S be the set of all positive integers having at most 4 digits and such that each of the digits is 0 or 1 What is the greatest prime factor of the sum of all the numbers in S?
问题求解PS -17760
The addition problem above shows four of the 24 different integers that can be formed by using each of the digits 1, 2, 3, and 4 exactly once in each integer. What is the sum of these 24 integers?
问题求解PS -17738
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?