Problem Solving

I have looked at this problem a million times and dont see how to get this answer.

Phone Company X has plan A and Plan B. Plan is is 0.60 cents per minute for the first 7 minutes and .06 cents per minute every minute afterwards. Plan B is .08 cents per minute fro all minutes. In minutes, when will plan A and plan B cost the same.

A. 7
B. 8
C. 9
D. 21
E. 30

Answer is C. Am i missing something here??

In this cases i'd rather do backsolving, much easier and faster.... By setting up the equation u'll lose at least 40 sec...

Yea but even using the answer, i dont get the same amount. using nine minutes I get $4.32 for Plan A and .72 cents for Plan B. Is this question jsut a typo....it was on the GMAC practice exam.

let x be the number of minutes.
Using Plan A
.6+(x-7).06 = total cost.

Using Plan B
.08x = total cost.since they are same,
.6+(x-7).06 = .08x
.6+.06x-.42 = .08x
or .18 = .02x therefore x=.18/.02 = 18/2 = 9 ans.

The possible mistake you could be making is computing the cost of plan A as .6+(x-1).06 but the cost of whole 7 minutes is .6 and not for the first minute.



Hope it helps.

Shouldn't the total cost using Plan A be

.6(7)+(x-7).06
because the question says

Plan A is is 0.60 cents PER MINUTE for the first 7 minutes and .06 cents per minute every minute afterwards

it says per minute

Thonk02 wrote:I have looked at this problem a million times and dont see how to get this answer.

Phone Company X has plan A and Plan B. Plan is is 0.60 cents per minute for the first 7 minutes and .06 cents per minute every minute afterwards. Plan B is .08 cents per minute fro all minutes. In minutes, when will plan A and plan B cost the same.

A. 7
B. 8
C. 9
D. 21
E. 30

Answer is C. Am i missing something here??

You copied the problem wrong. It is supposed to be ".60 for the FIRST 7 minutes of each call..."

Hence...why you can't come up with 9 as your answer.

According to the problem , the correct equation is:

7(.6)+(x-7)(.06)=x(.08)

there must be some kind of a typo in the problem.

cata1yst wrote:

Thonk02 wrote:I have looked at this problem a million times and dont see how to get this answer.

Phone Company X has plan A and Plan B. Plan is is 0.60 cents per minute for the first 7 minutes and .06 cents per minute every minute afterwards. Plan B is .08 cents per minute fro all minutes. In minutes, when will plan A and plan B cost the same.

A. 7
B. 8
C. 9
D. 21
E. 30

Answer is C. Am i missing something here??

You copied the problem wrong. It is supposed to be ".60 for the FIRST 7 minutes of each call..."

Hence...why you can't come up with 9 as your answer.

good, then 9 is the OA