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Question Involving Variables A01

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Question Involving Variables A01 [#permalink] New post 17 Nov 2011, 00:14
00:00
A
B
C
D
E

Difficulty:

  5% (low)

Question Stats:

57% (01:42) correct 43% (02:08) wrong based on 7 sessions
Just went through this question few days back. Though of posting this here. Not sure if this is a typical GMAT Question. But understanding this will help u

If K ltrs of a solution of x% milk, 2K ltrs of a solution of y% milk and 3K ltrs of a soulution of (x+y)% of milk are all mixed in a vessel, the resultant solution has 50% milk.
Find the resultant concentration of milk when 40 ltrs of the first soultion and 50 ltrs of the second solution are mixed.

A 40% B 33.33% C 50% D 53.33% E 60%
[Reveal] Spoiler: OA

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Re: Question Involving Variables A01 [#permalink] New post 17 Nov 2011, 00:20
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Here is the answer explanation.

The resultant concentration when the three solutions are mixed as given, will be
KX+2KY+3K(X+Y) / K+2K+3K = 4X+5Y/6 = 50% (Given)

Now, in the second case the resultant concentration will be 40x+50y/90 = 4x+5y/9

However, since 4x+5y/6 = 50% ,
4x+5y/9 = 50% * 2/3 = 33.33%

So Answer is B.
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Re: Question Involving Variables A01 [#permalink] New post 17 Nov 2011, 12:12
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The first equation is set up To be how much milk we have.

We have 6k liters of a solution, half of which is milk (as per prompt)

.5 x 6k = 3k

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Re: Question Involving Variables A01 [#permalink] New post 17 Nov 2011, 02:08
My approach:

kx + 2ky + 3kx + 3ky = 3k

Divide by k:
x + 2y + 3x + 3y = 3
4x + 5y = 3

Looks promising

40x + 50y = 30

30 / 90 = 1/3

B
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Re: Question Involving Variables A01 [#permalink] New post 17 Nov 2011, 03:43
pike wrote:
My approach:

kx + 2ky + 3kx + 3ky = 3k

Divide by k:
x + 2y + 3x + 3y = 3
4x + 5y = 3

Looks promising

40x + 50y = 30

30 / 90 = 1/3

B


Didnt understand this part :
kx + 2ky + 3kx + 3ky = 3k

why is Right hand side equal to 3k

This solution method seems to be easy and short. So plz explain the first part.
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Re: Question Involving Variables A01 [#permalink] New post 18 Nov 2011, 09:31
thanks
+1 to u.... But is this GMAT ind of problem. i posted this as the solution part was interesting
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Re: Question Involving Variables A01 [#permalink] New post 18 Nov 2011, 14:07
Yes I think this very GMAT-like

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Re: Question Involving Variables A01   [#permalink] 18 Nov 2011, 14:07
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