Mix problem

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Mix problem

by Mo2men » Mon Feb 15, 2016 12:17 pm
Compound P contains just three chemicals - X, Y, and Z. The three chemicals are required to be in the following ratio: 5 grams of X, 15 grams of Y, and z grams of Z. If 25 grams of X and a proportional amount of Y are added to the compound, what is the weight of Z that must also be added to maintain the required overall proportion?

(1) The weight of Compound P is always three times the weight of Z.
(2) The weight of Z is always twice the weight of X.
Source: — Data Sufficiency |

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by GMATGuruNY » Mon Feb 15, 2016 5:36 pm
Mo2men wrote:Compound P contains just three chemicals - X, Y, and Z. The three chemicals are required to be in the following ratio: 5 grams of X, 15 grams of Y, and z grams of Z. If 25 grams of X and a proportional amount of Y are added to the compound, what is the weight of Z that must also be added to maintain the required overall proportion?

(1) The weight of Compound P is always three times the weight of Z.
(2) The weight of Z is always twice the weight of X.
Compound P is composed of X, Y and Z in the following ratio:
x:y:z = 5:15:z.
To determine how much Z must be added when 25 grams of X are added, we need to know the value of z in the ratio above.

Statement 2: The weight of Z is always twice the weight of X
If x=5, then z=10, implying that x:y:z = 5:15:10.
SUFFICIENT.

Statement 1: The weight of Compound P is always three times the weight of Z.
The ratio yielded by Statement 1 is the only ratio that will satisfy Statement 2.
If x=5, y=15 and z=10, then P = x+y+z = 5+15+10 = 30, which is 3 times the value of z.
If z≠10, then the value of P will NOT be 3 times the value of z.
Thus, Statement 1 requires the same ratio as Statement 2:
x:y:z = 5:15:10.
SUFFICIENT.

The correct answer is D.
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