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• ### $450 Tuition Credit & Official CAT Packs FREE November 15, 2018 November 15, 2018 10:00 PM MST 11:00 PM MST EMPOWERgmat is giving away the complete Official GMAT Exam Pack collection worth$100 with the 3 Month Pack ($299) # M06-33  new topic post reply Question banks Downloads My Bookmarks Reviews Important topics Author Message TAGS: ### Hide Tags Math Expert Joined: 02 Sep 2009 Posts: 50576 M06-33 [#permalink] ### Show Tags 16 Sep 2014, 01:51 00:00 Difficulty: 15% (low) Question Stats: 89% (01:19) correct 11% (01:54) wrong based on 28 sessions ### HideShow timer Statistics 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? A. 8.33 B. 8.75 C. 9.23 D. 9.71 E. 10.07 _________________ Math Expert Joined: 02 Sep 2009 Posts: 50576 Re M06-33 [#permalink] ### Show Tags 16 Sep 2014, 01:51 Official Solution: 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? A. 8.33 B. 8.75 C. 9.23 D. 9.71 E. 10.07 The sum of the prices of all CD's is $$90 * 12 = 1,080$$. The sum of the prices of the most expensive CD's is$400. So, $$1,080 - 400 = 680$$ is left for 70 remaining CD's. Thus the average price is $$\frac{680}{70} = 9.71$$

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10 Jul 2018, 06:41
Hi chetan2u niks18 pushpitkc pikolo2510 Abhishek009

Is below approach (presumably of weighted average) valid:

[(20*20) + (x*70)] / 90 =12

Simplifying gives same result
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10 Jul 2018, 06:45
first we need to find total sum then subtract the most expensive ones and divide the rest
12*90=1080-400(20*20)=680/70=9.7 (D)
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10 Jul 2018, 07:25
Hi chetan2u niks18 pushpitkc pikolo2510 Abhishek009

Is below approach (presumably of weighted average) valid:

[(20*20) + (x*70)] / 90 =12

Simplifying gives same result

If you look closely, It is actually the same method as bunuel solved it.

Multiple by 90 on RHS and subtract 20*20 i.e.

x*70 = 90*12 - 20*20
x*70 = 1080 - 400
x*70 = 680
x = 680/70

x = 9.71
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Re: M06-33 &nbs [#permalink] 10 Jul 2018, 07:25
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# M06-33

Moderators: chetan2u, Bunuel

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