gwd math 22-29

sonniguy

这一题我有些不明白，哪位可否给我指教以下。谢谢了。

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?

 

A.     14

B.     15

C.     16

D.     28

E.      29

moo_moo_cow

1.5x > 13+0.6x; x > 130/9 > 14.444...

Hence the least value of x is 15. If x=15, 1.5x=22.5; 13+0.6x=22. If x=14, 1.5x=21; 13+0.6x=21.4.