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Will the first 10 volumes of a 20-volume encyclopedia fit

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Joined: 25 Dec 2011
Posts: 54
GMAT Date: 05-31-2012
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Kudos [?]: 18 [0], given: 29

Will the first 10 volumes of a 20-volume encyclopedia fit [#permalink] New post 26 Feb 2012, 02:55
00:00
A
B
C
D
E

Difficulty:

  35% (medium)

Question Stats:

73% (01:07) correct 27% (00:04) wrong based on 26 sessions
Attachment:
Bookrack.PNG
Bookrack.PNG [ 4.5 KiB | Viewed 1812 times ]
Will the first 10 volumes of a 20-volume encyclopedia fit upright in the bookrack shown above?

(1) x = 50 centimeters.
(2) Twelve of the volumes have an average (arithmetic mean) thickness of 5 centimeters.


[Reveal] Spoiler:
Hi please go through the attached file for the problem from gmat prep -

is it not a given that all the volumes of the book are of the same thickness so once you know

sum of the thickness of 12 volumes = given average x 12 = 60

then you can find the individual thickness = 5 !!

my answer was c

I find this strange at time - gmat assumes what it wants to but does not allow us to assume the obvious !
[Reveal] Spoiler: OA

Last edited by Bunuel on 26 May 2013, 04:21, edited 3 times in total.
Edited the question and added the figure
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Re: Will the first 10 volumes of a 20-volume encyclopedia fit [#permalink] New post 26 Feb 2012, 03:25
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Will the first 10 volumes of a 20-volume encyclopedia fit upright in the bookrack shown above?

(1) x = 50 centimeters. Clearly insufficient.

(2) Twelve of the volumes have an average (arithmetic mean) thickness of 5 centimeters. You most certainly can not assume that thickness of each of the 20 volumes is 5 centimeters, moreover you can not even assume that thickness of each of theses 12 volumes is 5 centimeters. Yes, the total thickness of these 12 volumes is 12*5=60 centimeters, but individual thicknesses could be {1, 1, 1, ..., 1, 49} or {2, 2, 2, ..., 2, 38} ... Next, you don't know which 12 volumes have an average thickness of 5 centimeters: first 12? last 12? first 6 and last 6? So, this statement is not sufficient.

(1)+(2) It's certainly possible that all 20 volumes to have thicknesses of 5 centimeters and in this case the first 10 volumes will fit in the bookrack of 50 centimeters but it's also possible that the last 12 volumes to have an average thickness of 5 centimeters and the first 8 volumes have thicknesses of 100 meters each (why not?) and in this case the first 10 volumes will NOT fit in the bookrack of 50 centimeters. Not sufficient.

Answer: E.

Hope it's clear.
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Re: Will the first 10 volumes of a 20-volume encyclopedia fit   [#permalink] 26 Feb 2012, 03:25
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