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标题: 问一道PREP题 [打印本页]

作者: chinabens    时间: 2006-3-7 07:28     标题: 问一道PREP题

Store S sold a toat of 90 copies of a certain book 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 the copies on Friady, did 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.

Answer: B

请问高手,如何快速地在2分钟内解出这题?我脑子有点膨胀。


作者: uniqueness    时间: 2006-3-7 20:00

设FRIDAY是X,因为每天都不同,使得X最小的情形是:38+x+x-1+x-2+x-3+x-4+x-5=90

6x=67

x=67/6>11


作者: chinabens    时间: 2006-3-11 10:18

thanks !!!!![em08]




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