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# m03: Q30

Author Message
Math Expert
Joined: 02 Sep 2009
Posts: 39037
Followers: 7750

Kudos [?]: 106476 [1] , given: 11626

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24 Jul 2013, 09:08
1
KUDOS
Expert's post
dragster88 wrote:
HI Karishma/Bunuel,

Could you please explain this problem with weighted avgs?

I did the problem using the weighted average method like below

w1/w2= [A2- A avrg]/[A avrg- A1]

A1- 2/5
A2- 3/10
A avrg- 5/16

i got w1/w2= 1/7

I conclude weight of first mixture as 1. But is this the right approach? Can you please confirm?

Check here: there-are-2-bars-of-gold-silver-alloy-one-piece-has-2-parts-48285.html

Karishma's approach: there-are-2-bars-of-gold-silver-alloy-one-piece-has-2-parts-48285.html#p890590

Hope it helps.
_________________
Intern
Joined: 16 Apr 2013
Posts: 3
Location: India
Concentration: Finance, Operations
GMAT Date: 08-14-2013
GPA: 4
WE: Analyst (Commercial Banking)
Followers: 0

Kudos [?]: 5 [0], given: 0

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24 Jul 2013, 18:40
Thanks a lot Bunuel.
Intern
Joined: 01 Jul 2013
Posts: 10
Location: India
Concentration: General Management, Technology
Followers: 0

Kudos [?]: 6 [0], given: 20

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24 Jul 2013, 21:23
Gold in bar 1 Gold in bar 2

2/5 3/10

5/16( Resultant mixture)
1/80 7/80
Ratio of gold : 1:7 , weight 8 kg
Therefore weight: 1kg.
Hence option A
Intern
Joined: 14 Oct 2013
Posts: 4
Concentration: Strategy, General Management
GMAT 1: 640 Q45 V32
WE: Management Consulting (Consulting)
Followers: 0

Kudos [?]: 1 [0], given: 12

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15 Jul 2014, 01:09
Okay - so here is how I did it without picking up my pen

New Bar - 8KG's anf G:S = 5:11 (5+11 = 16) So I took 8 KG's as 80 to make my life easy --> 80 = 16*5 so G:S = 25:55 .... (1)

Old bars are 2:3 and 3:7 - so we DEFINITELY know that the second bar has to be or a greater weight to get a 5:11 in the final bar - eliminated options C, D and E in my head

Check option A - if first bar is 10 KGs (remember I assumed 80 for 8KG) - G:S = 2:3 = 4KG:6KG
Remaining gold in final Bar of 80 KG = 25-4 = 21 KG
Second bar would be on 70KG (80-10) so in a ratio of 3:7 it will have 3*7 = 21KG gold

So 4 KG (from first bar) + 21 KG (second bar) = 25 KG (what we were looking for)

Re: m03: Q30   [#permalink] 15 Jul 2014, 01:09

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# m03: Q30

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