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by BTGmoderatorDC » Wed Sep 13, 2017 2:13 pm
X grams of water were added to 80 grams of a strong solution of acid. If as a result, the concentration of acid in the solution became 1/Y times of the initial concentration, what was the concentration of acid in the original solution?


(1) X = 80

(2) Y = 2

What is the best way to determine on which of the 2 statements are the correct answer?

OA E
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by Jay@ManhattanReview » Fri Sep 15, 2017 1:10 am
lheiannie07 wrote:X grams of water were added to 80 grams of a strong solution of acid. If as a result, the concentration of acid in the solution became 1/Y times of the initial concentration, what was the concentration of acid in the original solution?

(1) X = 80
(2) Y = 2

What is the best way to determine on which of the 2 statements are the correct answer?

OA E
Say out of 80 grams, the original solution had p grams of acid, thus, the original concentration of acid = p/80.

After the addition of x grams of water, the new concentration of acid = p/(80 + x)

We are given that

New concentration = 1/y * Original concentration

=> p/(80+x) = p/80y

y = 80/(80+x); 'p' cancels

The above equation suggests that even if we get the values of x and y, we cannot get the value of p/80, thus none of the statements are sufficient.

The correct answer: E

Hope this helps!

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-Jay
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