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## David has d books (OG16)

tagged by: Brent@GMATPrepNow

This topic has 2 expert replies and 0 member replies
boomgoesthegmat Senior | Next Rank: 100 Posts
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#### David has d books (OG16)

Thu May 19, 2016 3:45 pm
Elapsed Time: 00:00
• Lap #[LAPCOUNT] ([LAPTIME])
David has d books, which is 3 times as many as Jeff and 1/2 as many as Paula. How many books do the three of them have altogether, in terms of d ?

A) (5/6)d
B) (7/3)d
C) (10/3)d
D) (7/2)d
E) (9/2)d

OA: C

Last edited by boomgoesthegmat on Thu May 19, 2016 4:30 pm; edited 1 time in total

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Rich.C@EMPOWERgmat.com Elite Legendary Member
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Thu May 19, 2016 4:28 pm
Hi boomgoesthegmat,

To start, there's a typo in your transcription - it's supposed to read "...and 1/2 as many as Paula...."

We can answer this question by TESTing VALUES or by doing algebra...

IF...
Jeff = 2 books
David = 6 books = D books
Paula = 12 books

The total number of books = 2+6+12 = 20

So we're looking for an answer that equals 20 when D=6. There's only one answer that matches...

GMAT assassins aren't born, they're made,
Rich

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### GMAT/MBA Expert

Brent@GMATPrepNow GMAT Instructor
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Fri May 20, 2016 9:01 am
boomgoesthegmat wrote:
David has d books, which is 3 times as many as Jeff and 1/2 as many as Paula. How many books do the three of them have altogether, in terms of d ?

A) (5/6)d
B) (7/3)d
C) (10/3)d
D) (7/2)d
E) (9/2)d

OA: C
Rich has demonstrated the INPUT-OUTPUT approach. Here's an algebraic approach.

d = # of books that David has

David has 3 times as many books as Jeff
So, d/3 = # of books that Jeff has

David has 1/2 as many books as Paula
So, 2d = # of books that Paula has

How many books do the three of them have altogether, in terms of d ?
TOTAL # of books = d + d/3 + 2d
= 3d/3 + d/3 + 6d/3
= 10d/3
= C

---------------------------------

Rich and I have demonstrated the two methods (Algebraic and Input-Output) for solving a question type I call Variables in the Answer Choices.
If you'd like more information on these approaches, we have some videos:
- Variables in the Answer Choices - http://www.gmatprepnow.com/module/gmat-word-problems/video/933
- Tips for the Algebraic Approach - http://www.gmatprepnow.com/module/gmat-word-problems/video/934
- Tips for the Input-Output Approach - http://www.gmatprepnow.com/module/gmat-word-problems/video/935

Here are some more questions to practice with:
- http://www.beatthegmat.com/what-mistake-am-i-making-in-this-substitution-last-sunday-a-t276293.html
- http://www.beatthegmat.com/car-dealer-sales-t274136.html
- http://www.beatthegmat.com/ps-rate-times-t276107.html
- http://www.beatthegmat.com/to-find-the-least-perfect-square-t273338.html
- http://www.beatthegmat.com/y-dollars-from-the-rental-venture-t273031.html
- http://www.beatthegmat.com/meters-in-x-minutes-t273854.html

Cheers,
Brent

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