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28 Dec 2017, 00:10
00:00

Difficulty:

25% (medium)

Question Stats:

77% (01:49) correct 23% (02:11) wrong based on 27 sessions

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If John brought n comic books at $2 each, then brought m comic books at$7 each, and m- n comic books at $13 each, then the average (arithmetic mean) cost, in dollars per comic book, is equal to A. 22(m + n)/m B. (20m - 11n)/(2m) C. 11m D. (6m - 15n)/(2m - 2n) E. 22mn/(m + n) _________________ examPAL Representative Joined: 07 Dec 2017 Posts: 1072 Re: If John brought n comic books at$2 each, then brought m comic books  [#permalink]

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28 Dec 2017, 03:56
1
Bunuel wrote:
If John brought n comic books at $2 each, then brought m comic books at$7 each, and m- n comic books at $13 each, then the average (arithmetic mean) cost, in dollars per comic book, is equal to A. 22(m + n)/m B. (22m - 11n)/(2m) C. 11m D. (6m - 15n)/(2m - 2n) E. 22mn/(m + n) As all our values are small, we'll go for a straightforward calculation. This is a Precise approach. Total money spent is n*2 + m*7 + (m-n)*13 = m*20 - n*11 Total comic books purchased = n + m + (m-n) = 2m Average price per book is (m*20 - n*11)/2m. Bunuel are you sure the question is correct? If I'm not mistaken the coefficient of m should be 20 and not 22 in all relevant answers. (Or the question stem should be different) _________________ Math Expert Joined: 02 Sep 2009 Posts: 55719 Re: If John brought n comic books at$2 each, then brought m comic books  [#permalink]

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28 Dec 2017, 04:06
1
DavidTutorexamPAL wrote:
Bunuel wrote:
If John brought n comic books at $2 each, then brought m comic books at$7 each, and m- n comic books at $13 each, then the average (arithmetic mean) cost, in dollars per comic book, is equal to A. 22(m + n)/m B. (22m - 11n)/(2m) C. 11m D. (6m - 15n)/(2m - 2n) E. 22mn/(m + n) As all our values are small, we'll go for a straightforward calculation. This is a Precise approach. Total money spent is n*2 + m*7 + (m-n)*13 = m*20 - n*11 Total comic books purchased = n + m + (m-n) = 2m Average price per book is (m*20 - n*11)/2m. Bunuel are you sure the question is correct? If I'm not mistaken the coefficient of m should be 20 and not 22 in all relevant answers. (Or the question stem should be different) My mistake, you are right. Edited. Thank you. _________________ Board of Directors Status: QA & VA Forum Moderator Joined: 11 Jun 2011 Posts: 4504 Location: India GPA: 3.5 WE: Business Development (Commercial Banking) Re: If John brought n comic books at$2 each, then brought m comic books  [#permalink]

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28 Dec 2017, 09:30
Bunuel wrote:
If John brought n comic books at $2 each, then brought m comic books at$7 each, and m- n comic books at $13 each, then the average (arithmetic mean) cost, in dollars per comic book, is equal to A. 22(m + n)/m B. (20m - 11n)/(2m) C. 11m D. (6m - 15n)/(2m - 2n) E. 22mn/(m + n) $$\frac{2n + 7m + 13m - 13n}{m + n + m - n}$$ Or, $$\frac{20m - 11n}{2m}$$, answer will be (B) _________________ Thanks and Regards Abhishek.... PLEASE FOLLOW THE RULES FOR POSTING IN QA AND VA FORUM AND USE SEARCH FUNCTION BEFORE POSTING NEW QUESTIONS How to use Search Function in GMAT Club | Rules for Posting in QA forum | Writing Mathematical Formulas |Rules for Posting in VA forum | Request Expert's Reply ( VA Forum Only ) Re: If John brought n comic books at$2 each, then brought m comic books   [#permalink] 28 Dec 2017, 09:30
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