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solution X and Y

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by charmaine » Thu Sep 11, 2008 5:52 pm
Solution Y is 30 percent liquid X and 70 percent water. If 2 kilograms of water evaporate from 8 kilograms of solution Y and 2 kilograms of solution Y are added to the remaining 6 kilograms of liquid, what percent of this new solution is liquid X?

answer: 37 1/2%

thanks for the help :)
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by superbrat123 » Thu Sep 11, 2008 8:16 pm
In 8 kilogram solution of Y
x=30% of 8 = 2.4, water = 70% of 8 = 5.6
Now, 2 kilogram of water is evaporated => 5.6-2.0 = 3.6

In 2 kilogram solution of Y, x=30%of2 = 0.6, water = 70%of2=1.4

In the final solution, we have
x = 2.4+0.6, total water = 3.6+1.4

x as percent of x+water = 3.0/3.0+5.0 = 3/8 = 37.5%
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by cramya » Fri Sep 19, 2008 7:07 pm
Convert the kilograms to grams (1kg = 1000g) Since we are asked percent it doesnt change. Even if the question was what kg of x is present in the final solution its an easy divide by 1000

It may be easy to work with in 2 minutes. Just my opinion!! Good luck!
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by gmatt14 » Fri Oct 15, 2010 7:36 am
Most importantly, we have to concentrate on what is being asked! If you concentrate solely on X, you can solve this question fast.

Consider the attached table, which helped me out a lot to grasp this concept.

From the table we gain the equation:

0.3 (8) + 0.3 (2) = 0.3 (8+2) = 0.3 (10) = 3

8 kg of solution Y contains 3 kg of solution X:

3/8 = 37.5 %

Hope this helps! ;-)
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by GMATGuruNY » Fri Oct 15, 2010 12:28 pm
The water that is being replaced is 2/8 = 25% of the total solution. We are replacing this 25% with solution Y. Thus, the percentage of liquid X in the total solution is going to increase by 25%:

1.25*30 = 37.5.

The correct answer is D.

Similarly, if the water being replaced were 4/8 = 50% of the total solution, the percentage of liquid X would increase by 50% in the resulting solution. The resulting solution would be 1.5*30 = 45% X and 55% water.
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