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# Comparison of payment plan of telephone company

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Manager
Joined: 04 May 2009
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Comparison of payment plan of telephone company [#permalink]

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28 Mar 2010, 08:59
00:00

Difficulty:

(N/A)

Question Stats:

25% (00:34) correct 75% (02:04) wrong based on 4 sessions

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That problem seemed easy but never figured the correct answer, not even with solution provided.... help!

A telephone company offers two plans, A and B. Under plan A, the company charges a total of \$0.90 for the first 7 minutes and \$0-06 per min thereafter. Under plan B, the company charges \$0.08 per min of each call. What is the duration of a call, in minutes, for which the company charges the same amount under plan A and under plan B?
A: 2
B: 9
C:15
D:21
E:30

[Reveal] Spoiler:
OA = B

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Re: Comparison of payment plan of telephone company [#permalink]

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28 Mar 2010, 12:15
1
KUDOS
I think this problem has a typo. If you can, go back to the original GMATPrep screen to verify.

If the answer is as given, I think the problem would have to read "A telephone company offers two plans, A and B. Under plan A, the company charges a total of \$0.60 for the first 7 minutes and \$0.06 per min thereafter. Under plan B, the company charges \$0.08 per min of each call. What is the duration of a call, in minutes, for which the company charges the same amount under plan A and under plan B?"

For the problem as written above, I get 24 as the answer. The equation (amounts in cents, for ease of calculation) is 90 + 6(x-7) = 8x, where x is the number of minutes.

90 + 6x - 42 = 8x
48 = 2x
x = 24
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Senior Manager
Joined: 01 Feb 2010
Posts: 251

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Re: Comparison of payment plan of telephone company [#permalink]

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28 Mar 2010, 22:30
nifoui wrote:
That problem seemed easy but never figured the correct answer, not even with solution provided.... help!

A telephone company offers two plans, A and B. Under plan A, the company charges a total of \$0.90 for the first 7 minutes and \$0-06 per min thereafter. Under plan B, the company charges \$0.08 per min of each call. What is the duration of a call, in minutes, for which the company charges the same amount under plan A and under plan B?
A: 2
B: 9
C:15
D:21
E:30

[Reveal] Spoiler:
OA = B

x - number of minutes for a call
0.9 + .06(x-7) = 0.08x
0.02x = 0.48
x=24

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Intern
Joined: 23 Feb 2010
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Re: Comparison of payment plan of telephone company [#permalink]

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28 Mar 2010, 23:23
I defined the variable a little differently because I find I make more mistakes when I subtract than add (for whatever reason). I set "x" to be the number of minutes after the first 7 (which assumed the call would be more than 7 minutes but I figured that was a safe assumption for the question).

0.9 + 0.06x = 0.08(x+7)
0.02x = 0.34
x = 17
Add the first 7 minutes: 17 + 7 = 24 minutes.

Something's off with the question/answer set, just wanted to add a different way to define the variable.

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Intern
Joined: 03 Sep 2010
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Re: Comparison of payment plan of telephone company [#permalink]

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08 Oct 2010, 21:18
Hi,
Lets take the money in cents and minutes as M.
then
60+(M-7)6=8M
i.e 60+6M-42=8M
2M=18 and hence M=9

So the answer is 9 Minutes. Even i got this wrong in the test,But taking my time and solving this helped figure out the solution.

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Intern
Joined: 12 Oct 2010
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Re: Comparison of payment plan of telephone company [#permalink]

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12 Oct 2010, 13:39
srihariom wrote:
Hi,
Lets take the money in cents and minutes as M.
then
60+(M-7)6=8M
i.e 60+6M-42=8M
2M=18 and hence M=9

So the answer is 9 Minutes. Even i got this wrong in the test,But taking my time and solving this helped figure out the solution.

But they charge \$.90 for the first 7 minutes, not \$.06

So taking it in cents would be 90+(M-7)6=8M, right?

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Re: Comparison of payment plan of telephone company   [#permalink] 12 Oct 2010, 13:39
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