gwd18-23

[vickyhung]

The toll for crossing a certain bridge is $0.75 each crossing.Drivers who frequently use the bridge instead 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 Xdays next month and will not cross the bridge on any other day,what is the least value of Xfor which this driver can save money by using the sticker?

做不出來....可以請各位大大幫忙嗎??
感恩......

[scujean]

1.題號沒有標清楚 2.題目沒貼完整

The toll for crossing a certain bridge is $0.75 each crossing.Drivers who frequently use the bridge instead 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 Xdays next month and will not cross the bridge on any other day,what is the least value of Xfor which this driver can save money by using the sticker?
A. 14
B. 15
C. 16
D. 28
E. 29

每次過路費是0.75元。 開車的人買$13的票 每次經過再支付0.3元 。如果某司機將會過此橋2倍的x天 ,其他天不會經過此橋 求最小的x

cd’s ans:
1.5x大于13＋0.6x，解这个不等式就是了，x取整。1.5=0.75*2
觀念是，[買票的變動+固定成本 ]至少要小於 不買票的變動成本