For a basic monthly fee of F yen, Noak's first cell phone allowed him

Question

For a basic monthly fee of F yen, Noako's first cell phone allowed him to use a maximum of 420 minutes on calls during the month. Then, for each of x additional minutes he used on calls, he was charged M yen, making his total charge for the month T yen, where T = F + xM. What is the value of M?

(1) Naoko used 450 minutes on calls the first month and the total charge for the month was 13, 755 yen

(2) Naoko used 400 minutes on calls the second month and the total charge for the month was 13, 125 yen

This version of the question is different from DS #278 in OG2017

JeffTargetTestPrep · Accepted Answer

We are given T = F + xM, in which T = the total charge for the month, F = the monthly fee, x = the excess minutes over 420, and M = the amount charged for each of the x additional minutes.

Statement One Alone:

Naoko used 450 minutes on calls the first month, and the total charge for the month was 13,755 yen.

Using the information in statement one, we can determine that Naoko used 30 excess minutes beyond the 420 minutes allowed by the basic monthly fee, so we can create the following equation:

13,755 = F + 30M

However, since we don’t know the value of F, we do not have enough information to determine the value of M. Statement one alone is not sufficient to answer the question. We can eliminate answer choices A and D.

Statement Two Alone:

Naoko used 400 minutes on calls the second month and the total charge for the month was 13,125 yen.

Since 400 < 420, we know that 13,125 yen must be the basic monthly free. That is,

13,125 = F

However, we still do not have enough information to determine the value of M. Statement two alone is not sufficient to answer the question. We can eliminate answer choice B.

Statements One and Two Together:

From statements one and two we have the following equations:

13,755 = F + 30M

AND

13,125 = F

Thus, we have:

13,755 = 13,125 + 30M

630 = 30M

21 = M

Answer: C

pkbharkhada · Answer

The official question from OG 2017 (Question 278) is asking for value of F but the question posted on this forum is asking for M, hence the confusion between B and C. The OA is B.

msk0657 · Answer

We are given , for a basic F yen , Noak can talk till 420 minutes and he'll be charged beyond 420 minutes. For every X additional minutes there will be M yen charged.

From

Stat 1) 13755 = F + 30M --> Insufficient. As we don't know F value. ( X = 30 ( 450 - 420 ) here because he crossed beyond 420 )

Stat 2) 13125 = F + 0 (M). Here only 400 minutes and he don't have any extra minutes to be charged, hence 0 mins.

Then F = 13125. --> Insufficient... don't have M value.

Stat 1 + Stat 2 : 13755 = 13125 + 30 M.
 => 630 = 30 M
 M = 23.

Option C is correct answer.

kristine0912 · Answer

The correct answer here is B because statement 2 alone is sufficient. 
The question stem does not specify for which month you need to find T

mikemcgarry · Answer

Dear kristine0912 , I saw your report and I am happy to respond. :-)

My friend, with all due respect, I disagree with your conclusion. (B) is not sufficient by itself. You see, we want the value of M, the fee for extra minutes above 420 minutes. If we are considering (B) alone and by itself, (B) gives us the process for a time less than 420 minutes. (B) allows us to figure out directly that F = 13,125 yen. That's great, very valuable, but that doesn't answer the prompt question. We want M, not F. We need to take that valuable information from (B) back to the additional information in (A) in order to find the value of M. That's why the answer is (C). Does all this make sense? Mike :-)

Bunuel · Answer

I posted OG question, which has B as the OA here: https://gmatclub.com/forum/for-a-basic- ... 43064.html

msk0657 · Answer

Everyone,

Please see the question.  This specific question is asking for the value of M and the one that Bunuel posted is asking for the value of F. 
I didn't see the official question yet.  Both questions can be treated differently and answers are different. So solve accordingly.

zvazviri · Answer

For those who actually go all the way to solve for M, it's nice, but that's not the question. Just showing 2 equations with the same 2 variables is sufficient to answer the question. Why waste time doing the unnecessary?

C is the answer.

C is the answer.

mpmbtr · Answer

Thanks for the question and for the answers!

nust2017 · Answer

That's why on the Error log of OG 2018, the OA is coming as B while for this question the OA is C.

AN12 · Answer

Can the error log of OG 2019 for this question be updated? As official answer is taken as B instead of C.

Posted from my mobile device

eantolovic · Answer

Hi All,

I understand that we cannot entertain Option C until we determined if Option A, Option B, or both individually can answer the question. Option B (Statement II), announces M=0. Depending on how one interprets the question will determine how one deems that to be correct, or to just assume the question is asking for the value of M in the scenario presented in Statement I, which is the first billing month.

In any case, the question seems to be loopholed enough for us to be certain not to go too deep into the rabbit hole on it, and to just rely on the re-posting of the correctly-phrased question by Bunuel

MHIKER · Answer

(1) No information for additional minutes over 420 is given. Insufficient.

(2) Information is not given whether he used additional minutes. Insufficient.

Considering both:

Naoko used 450 minutes, for 400 minutes he paid 13,125, his limit was 420 after that he pay the additional charge.

Additinal minutes 450-420=30, additional charge 13,755-13,125=630, value of M=630/30; Sufficient.

The answer is C.

GMATinsight · Answer

Answer: Option C

Video solution by  GMATinsight

https://www.youtube.com/watch?v=48W26qmSfcg

CrackverbalGMAT · Answer

Statement 1: 13,755 = F + 30 M
Statement 1 is clearly not sufficient as we are not able to get the value of M

​St 2: Since Naoko used only 400 minutes (<420 min ) on calls the second month, he will charged only the monthly fee ,F.

F = 13,125 
St 2 alone is not sufficient to get the value of M.

Combining 1 and 2 , we can get a definite value for M.

Option C is the answer.

Thanks,
Clifin J Francis,
GMAT SME

bumpbot · Answer

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For a basic monthly fee of F yen, Noak's first cell phone allowed him

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