本月数学鸡 264完全不明白是怎么做呀~~HELP~~~

irenezlc

264: Jane (人名是我随便编的) is to pay 5 bills, and the 5 bills are with different amounts. If Jane is to pay the greatest amount bill first and the least amount bill last... what is the possibility she has?  答案都是分数。。。

   3！/ 5! = 1/20

不明白题目问题是什么意思？？？

xxgoodluck

If Jane pays her bills in random order: A(5,5)
If Jane pays the greatest bill first, the lease amount bill last, it means only the rest three need to be put into order: A(3,3).

Then, the possibility should be A(3,3)/A(5,5).

Hope this helps~ Good luck^^

sdcar2010

Greatest M M M Least

If pay as above, 3!

If total random, 5!

irenezlc

If Jane pays her bills in random order: A(5,5)
If Jane pays the greatest bill first, the lease amount bill last, it means only the rest three need to be put into order: A(3,3).

Then, the possibility should be A(3,3)/A(5,5).

Hope this helps~ Good luck^^

-- by 会员 xxgoodluck (2010/11/12 10:49:37)

Thank you very much! I got it ~~

irenezlc

Greatest M M M Least

If pay as above, 3!

If total random, 5!

-- by 会员 sdcar2010 (2010/11/12 10:53:14)

thanks a lot ~~~