UC知道求OG 数学一道题的解析!!
来源：百度知道 编辑：UC知道 时间：2024/06/17 20:56:38
31. In the table above, what is the least number of table entries that are needed to show the mileage between each city and each of the other five cities?
(A)15 (B)21 (C)25 (D)30 (E)36
图在http://www.examda.com/GRE/Guide/20070329/102934150.html
31题,有点不太明白这道题意思的说!!
答案是A~~哪位高人解释下啊
答案分析是:
since there is no mileage between a city and itself, and since the mileage for each pair of cities needs to be completed only once, only these boxes below or above the diagonal from the upper left to the lower right need to be counted.
the gives 1+2+3+4+5=15
(A)15 (B)21 (C)25 (D)30 (E)36
图在http://www.examda.com/GRE/Guide/20070329/102934150.html
31题,有点不太明白这道题意思的说!!
答案是A~~哪位高人解释下啊
答案分析是:
since there is no mileage between a city and itself, and since the mileage for each pair of cities needs to be completed only once, only these boxes below or above the diagonal from the upper left to the lower right need to be counted.
the gives 1+2+3+4+5=15
很简单啊，六个城市，选择俩俩对应，C62（前下标，后上标）。c62=6*5/2=15
用概率论或者运筹学就可以解出了。
5+4+3+2+1那个方法是用一一对应的那个对角线法解得，比较木。但是最后还是能推出C法的。