一道数学题，求救？

sunnycc · 发表于 2011-9-22 10:11:02

Store S sold a total of 90 copies of a certain bood during the seven days of last week, and it sold different numbers of copies on any two of the days. If for the seven days Store S sold the greatest number of copies on Saturday and the second greatest number of copies on Friday, did the Store S sell more than 11 copies on Friday?
1)last week Store S sold 8 copies of the book on Thursday
2)last week Store S sold 38 copies of the book on Saturday
答案：B

没有思路，哪们NN有解题方法

sunnycc · 发表于 2011-9-22 10:13:29

自己顶！

sunnycc · 发表于 2011-9-22 10:17:00

没有回答吗？呜呜

超级无敌小鹤鹤 · 发表于 2011-9-22 10:22:23

确实是B

wellizsm · 发表于 2011-9-22 10:24:01

1) Thursday卖出8本只能说明Friday卖出多于8本不充分
2) Saturday卖出38本那么剩余6天总共卖了52本此时如果Friday卖出不多于11本又由于每天卖出的数量不同那么6天最多只能卖11+10+9+8+7+6=51本所以 Friday必须卖出多于11本

sunnycc · 发表于 2011-9-22 10:30:40

I got it.
Thanks a lot!

一道数学题，求救？

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