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Mixture Question

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by smclean23 » Mon Jul 07, 2008 4:04 pm
# of calories per kilogram # of grams of protein per kilogram
S 2,000 150
T 1,500 90

20. The table above gives the number of calories and grams of protein per kilogram of foods S and T. If a total of 7 kilograms of S and T are combined to make a certain food mixture, how many kilograms of food S are in the mixture?
(1) The mixture has a total of 12,000 calories.
(2) The mixture has a total of 810 grams of protein.
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Source: — Data Sufficiency |

by lion147 » Mon Jul 07, 2008 4:13 pm
The answer is D (IMHO).

I setup equations for each statement like so:

1) 2000S + 1500T = 12000
S + T = 7
T = 7 - S
2000S + 1500(7-S) = 12000
2000S + 10500 - 1500S = 12000
500S = 1500
S = 3

2) 150S + 90T = 810
S + T = 7
T = 7 - S
150S + 90(7-S) = 810
150S + 630 - 90S = 810
60S = 180
S = 3
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by mim3 » Fri Jul 11, 2008 12:25 pm
Agreed- it's D. IMHO, you don't even need the equations. From the stem, we have one equation already: S+T= 7. So we know we only need one other unique equation to get S which both statements give us, so both are sufficienton their own.
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