【SAT每日一题】2012年7月20 Mathematics > Standard Multiple Choice
考试类型: Mathematics > Standard Multiple ChoiceRead the following SAT test question and then click on a button to select your answer.
In an http://sat.collegeboard.org/mathmlgen/content/question/QOTD/2012/20120720_1.png solution of water and alcohol, the ratio by mass of water to alcohol is 3 to1 . If 12 grams of a solution consisting of 2 grams water for each gram of alcohol is added to the http://sat.collegeboard.org/mathmlgen/content/question/QOTD/2012/20120720_6.pngsolution, what fraction by mass of the new solution is alcohol?
A. http://sat.collegeboard.org/mathmlgen/content/question/QOTD/2012/20120720_7.png
B. http://sat.collegeboard.org/mathmlgen/content/question/QOTD/2012/20120720_8.png
C. http://sat.collegeboard.org/mathmlgen/content/question/QOTD/2012/20120720_9.png
D. http://sat.collegeboard.org/mathmlgen/content/question/QOTD/2012/20120720_10.png
E. http://sat.collegeboard.org/mathmlgen/content/question/QOTD/2012/20120720_11.png
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 20 grams. Since the http://sat.collegeboard.org/mathmlgen/content/question/QOTD/2012/20120720_14.png solution is 1 part alcohol to 3 parts water, it is http://sat.collegeboard.org/mathmlgen/content/question/QOTD/2012/20120720_17.png alcohol. So it 2contains grams of alcohol. Similarly, the http://sat.collegeboard.org/mathmlgen/content/question/QOTD/2012/20120720_19.png solution is http://sat.collegeboard.org/mathmlgen/content/question/QOTD/2012/20120720_20.pngalcohol by mass, so it contains 4 grams of alcohol. Thus, the final http://sat.collegeboard.org/mathmlgen/content/question/QOTD/2012/20120720_22.png solution contains 6 grams of alcohol, so , http://sat.collegeboard.org/mathmlgen/content/question/QOTD/2012/20120720_24.pngorhttp://sat.collegeboard.org/mathmlgen/content/question/QOTD/2012/20120720_24.png , of it is alcohol.
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