Data Sufficiency

A contractor combined x tons of a gravel mixture that contained 10% gravel G, by weight, with y tons of a mixture that contained 2 percent of the gravel G, by weight, to produce z tons of a mixture that was 5 percent gravel G, by weight. What is the value of x?

1) y = 10

2) z = 16

Using the "tug of war" method, we can figure out the ratio of X to Y from the stem alone:

Y X
2--5----10

5-2 = 3

10-5 = 5

X:Y = 3:5

Now we just need something that will allow us to go from a proportion to an exact value.

1) Perfect! Using the ratio above, we can determine that x is 6.

2) This works as well. From the stem, we can set up the equation .1x + .02y = .05(z), and S2 gives us the equation x + y = 16. We can solve two independent linear equations.

D