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# Some part of the 50% solution of acid was replaced with the

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Manager
Joined: 21 Feb 2008
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Some part of the 50% solution of acid was replaced with the [#permalink]

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21 Oct 2008, 11:41
This topic is locked. If you want to discuss this question please re-post it in the respective forum.

Some part of the 50% solution of acid was replaced with the equal amount of 30% solution of acid. As a result, 40% solution of acid was obtained. What part of the original solution was replaced?

A. $$\frac{1}{5}$$

B. $$\frac{1}{4}$$

C. $$\frac{1}{2}$$

D. $$\frac{3}{4}$$

E. $$\frac{4}{5}$$

Answer is C. It's relatively easy to understand why 1/2 is correct but I can't logically put an equation together to solve the question.
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21 Oct 2008, 13:16
duuuma wrote:
Some part of the 50% solution of acid was replaced with the equal amount of 30% solution of acid. As a result, 40% solution of acid was obtained. What part of the original solution was replaced?

A. $$\frac{1}{5}$$

B. $$\frac{1}{4}$$

C. $$\frac{1}{2}$$

D. $$\frac{3}{4}$$

E. $$\frac{4}{5}$$

Answer is C. It's relatively easy to understand why 1/2 is correct but I can't logically put an equation together to solve the question.

x is part of solution replaced

0.5 (1-x) +0.3*x = 0.4*1

x=1/2
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21 Oct 2008, 14:10
0.5 (1-X) + 0.3X = 0.4
X = 1/2

CANNOT ADD ANYTHING TO ABOVE SOL.
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Manager
Joined: 21 Feb 2008
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Schools: UCLA Anderson '12
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21 Oct 2008, 14:48
Not sure I understand your comment. What do you mean by, "cannot add anything..."?
GMAT TIGER wrote:
0.5 (1-X) + 0.3X = 0.4
X = 1/2

CANNOT ADD ANYTHING TO ABOVE SOL.
SVP
Joined: 29 Aug 2007
Posts: 2476
Followers: 70

Kudos [?]: 774 [0], given: 19

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21 Oct 2008, 16:39
duuuma wrote:
Not sure I understand your comment. What do you mean by, "cannot add anything..."?
GMAT TIGER wrote:
0.5 (1-X) + 0.3X = 0.4
X = 1/2

CANNOT ADD ANYTHING TO ABOVE SOL.

I meant "CANNOT ADD ANYTHING TO THE ABOVE SOL.by "x2suresh". Is it clear now, "duuuma"?
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Manager
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21 Oct 2008, 16:49
I'm guessing you meant that you agree with his solution and cannot add anything on top of that? Makes sense - thanks

GMAT TIGER wrote:

I meant "CANNOT ADD ANYTHING TO THE ABOVE SOL.by "x2suresh". Is it clear now, "duuuma"?
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21 Oct 2008, 18:31
duuuma wrote:
I'm guessing you meant that you agree with his solution and cannot add anything on top of that? Makes sense - thanks

GMAT TIGER wrote:

I meant "CANNOT ADD ANYTHING TO THE ABOVE SOL.by "x2suresh". Is it clear now, "duuuma"?

you got it, duuuma.
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Re: Difficult Ratio question   [#permalink] 21 Oct 2008, 18:31
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