The Official SAT Question of the Day™

Read the following SAT test question, then click on a button to select your answer.


In an 8-gram solution of water and alcohol, the ratio by mass of water to alcohol is 3 to 1. If 12 grams of a solution consisting of 2 grams water for each gram of alcohol is added to the 8-gram solution, what fraction by mass of the new solution is alcohol?

A 1/6
B 3/10
C 5/12
C 7/12
D 5/24

Answer is B

Here's Why:

To find what fraction by mass of the new solution is alcohol, you can find how many grams of alcohol are in the final solution of 20 grams. Since the 8-gram solution is 1 part alcohol to 3 parts water, it is 1/4 alcohol. So it contains 2 grams of alcohol. Similarly, the 12-gram solution is 1/3 alcohol by mass, so it contains 4 grams of alcohol. Thus, the final 20-gram solution contains 6 grams of alcohol, so 6/20, or 3/10, of it is alcohol.


Difficulty: Hard
Question Type: Standard Multiple Choice

(Mathematics)