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SAT官方每日一题附答案和解析[数学](2015年10月19日)
日期:2015-10-19 14:13

(单词翻译:单击)

每日一题

Mathematics>Standard Multiple Choice

Read the following SAT test question and 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
(D) 7/12
(E) 5/24

答案和解析

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 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.

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重点单词
  • massn. 块,大量,众多 adj. 群众的,大规模的 v.
  • solutionn. 解答,解决办法,溶解,溶液
  • alcoholn. 酒精,乙醇,酒
  • multipleadj. 许多,多种多样的 n. 倍数,并联
  • fractionn. 分数,小部分,破片