A music store has 90 different CD's : GMAT Problem Solving (PS)
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# A music store has 90 different CD's

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Senior Manager
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Joined: 15 Sep 2010
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A music store has 90 different CD's [#permalink]

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29 Sep 2011, 09:10
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0% (00:00) correct 100% (00:46) wrong based on 3 sessions

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Q) A music store has 90 different CD's. If an average price is $12 per CD and 20 of the most expensive ones are$20 each, what is the average price of the remaining CD's?

[Reveal] Spoiler:
9.71

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I'm the Dumbest of All !!

Intern
Joined: 24 Sep 2011
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Re: A music store has 90 different CD's [#permalink]

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29 Sep 2011, 16:06
1
KUDOS
[(20)(20)+(70)(X)]/90 = 12
400 + 70X = 1080
70X = 680
X = 9.71
Director
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Re: A music store has 90 different CD's [#permalink]

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29 Sep 2011, 20:13
(x1+x2+....x70+ (20*20)) /90 = 12

=> x1+x2+....x70 = 680

=> average of the above 70 numbers = 680/70 = 9.71
Manager
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Re: A music store has 90 different CD's [#permalink]

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01 Oct 2011, 01:07
easy one .. ( (90*12) - (20*20) ) / (90-20) = 9.71
_________________

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
MGMAT 6 650 (51,31) on 31/8/11
MGMAT 1 670 (48,33) on 04/9/11
MGMAT 2 670 (47,34) on 07/9/11
MGMAT 3 680 (47,35) on 18/9/11
GMAT Prep1 680 ( 50, 31) on 10/11/11

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CR notes
http://gmatclub.com/forum/massive-collection-of-verbal-questions-sc-rc-and-cr-106195.html#p832142
http://gmatclub.com/forum/1001-ds-questions-file-106193.html#p832133
http://gmatclub.com/forum/gmat-prep-critical-reasoning-collection-106783.html
http://gmatclub.com/forum/how-to-get-6-0-awa-my-guide-64327.html
http://gmatclub.com/forum/how-to-get-6-0-awa-my-guide-64327.html?hilit=chineseburned

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Re: A music store has 90 different CD's [#permalink]

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01 Oct 2011, 01:42
Price= 10(9*12-2*20)/70
=(108-40)/7
68/7
9.71
Re: A music store has 90 different CD's   [#permalink] 01 Oct 2011, 01:42
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