This question asks: Baxter is mixing a concentrated pigment with a solvent in the ratio of 2:9. If he has 3(3/4) gallons of the pigment, how many gallon cans of solvent will he need to use up all the pigment?

A) 9
B) 15
C) 17
D) 34
E) Other

The correct answer is "C)". I answered "E) Other" because my answered indicated somewhere around 10 gallons of solvent. Here I started with the ratio 2 pigment for 9 solvent. I attempted to cross-multiply where I:
[multiply 9 solvent with 3(3/4) pigment] divided by [2 pigment]...which should give me the answer by the number of solvent required for the 3(3/4) pigment.

Is my understanding of the cross-multiplication incorrect here? I simply wanted to obtain the right amount of solvent required while respecting the pigment's 2:9 ratios.

I'm sorry for asking so many questions on the pre-test. I should now be ready to start my day 1 course and I will be taking my simulated GMAT prior to this class. Thanks a lot for your help!


Matt

We know that pigment / solvent = 2/9
or P/S = 2/9

We then convert 3 3/4 to a single fraction, and it becomes 15/4

Now we have P/s = 15/4 / S = 2/9
We can cross multiply, and we get
2S = 9*15/4
2S = 135/4
S = 135/8
S = between 16 and 17.
Thus, we need 17 cans to make this work.

Hope this helps,

Veritas Help

I understand. My mistake was forgetting to convert 3 and 3/4 gallons into fractions (i.e. 15/4). Thanks a lot for your help!