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28 Dec 2017, 00:10
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Difficulty:

25% (medium)

Question Stats:

76% (00:58) correct 24% (01:06) wrong based on 24 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: 417 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) _________________ David Senior tutor at examPAL Signup for a free GMAT course We won some awards: Join our next webinar (free) Save up to$250 on examPAL packages (special for GMAT Club members)

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Re: If John brought n comic books at $2 each, then brought m comic books [#permalink] ### Show Tags 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.
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Re: If John brought n comic books at $2 each, then brought m comic books [#permalink] ### Show Tags 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)
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Abhishek....

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