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标题: 一道2005 9月51题 [打印本页]

作者: inlovesummer 时间: 2006-8-7 22:10
标题: 一道2005 9月51题

51.

The toll for crossing a certain bridge is $0.75 each crossing. Drivers who frequently use the bridge may instead purchase a sticker each month for $13.00 and then pay only $0.30 each crossing during that month. If a particular driver will cross the bridge twice on each of x days next month and will not cross the bridge on any other day, what is the least value of x for which this driver can save money by using the sticker?

A. 14

B. 15

C. 16

D. 28

E. 29

SA:B 怎样做的啊..........

http://forum.chasedream.com/dispbbs.asp?boardID=22&ID=131409&page=1

作者: lovetiky 时间: 2006-8-7 22:51

x*2*0.75 > 13+x*2*0.3

x > 13/0.9=14.4

x = 15

[此贴子已经被作者于2006-8-8 17:10:42编辑过]

作者: CrystalLion 时间: 2006-8-8 16:28

题目中不是说 driver will cross the bridge twice on each of x days？

是否应该是 x*2*0.75〉13+x*2*0.3?

作者: nebelstreif 时间: 2006-8-8 17:09
答案是B吧。

作者: lovetiky 时间: 2006-8-8 17:10

以下是引用CrystalLion在2006-8-8 16:28:00的发言：

题目中不是说 driver will cross the bridge twice on each of x days？

是否应该是 x*2*0.75〉13+x*2*0.3?

对!

已经改过来了

谢谢CrystalLion!!

作者: gonghao 时间: 2006-8-8 17:15

以下是引用CrystalLion在2006-8-8 16:28:00的发言：

题目中不是说 driver will cross the bridge twice on each of x days？

是否应该是 x*2*0.75〉13+x*2*0.3?

correct!

作者: lovetiky 时间: 2006-8-8 17:19

这下被大家鄙视了~~

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