[求助]TTGWD-15-22, 不明白

3Flady

Q29:???????????????????????????

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?

 答案是B? 不明白题目是什么意思? 谢谢NN指点

A.    14

B.     15

C.     16

D.    28

E.     29

snoopydior

就是一个不等式求解

x天每天过两次

不买sticker需要钱数：0.75*2*x

买sticker后需要钱数：0.3*2*x+13

如果买sticker省钱的话即：0.3*2*x+13<=0.75*2*x

解除x=14.4 选15

这么说lz明白了？

3Flady

谢谢楼上, 原来是题目读错了, 以为是买了个13$的卡,每次从卡里划钱呢...