PS

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PS

by ketkoag » Sat Mar 28, 2009 2:22 am
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

My exact answer is 14.44 please tell me how to select the answer.
OA : B
I used the equation: (.75*2)x > 13+.30*2*x
Please explain.....
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by moutar » Sat Mar 28, 2009 2:39 am
To break even:

(.75*2)x = 13 + .30*2*x
1.5x = 13 +0.6x
0.9x = 13
= 13/0.9 = 14.444

For any days less than that they would lose money so we pick the number of days that is more which is B. 15.