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2011年8月23日
考试类型:Mathematics > Standard Multiple Choice
Read the following SAT test question and then click on a button to select your answer.
In an 
solution of water and alcohol, the ratio by mass of water to alcohol is 
to 
. If 
grams of a solution consisting of 
grams water for each gram of alcohol is added to the 
solution, what fraction by mass of the new solution is alcohol?
A. 
B. 
C. 
D. 
E. 
正确答案:B
解析:
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 
grams. Since the 
solution is 
part alcohol to 
parts water, it is 
alcohol. So it contains 
grams of alcohol. Similarly, the 
solution is 
alcohol by mass, so it contains 
grams of alcohol. Thus, the final 20-gram solution contains 
grams of alcohol, so 
, or 
, of it is alcohol.