[外语类试卷]GRE（QUANTITATIVE）练习试卷14及答案与解析.doc

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1、GRE（ QUANTITATIVE）练习试卷 14及答案与解析 1 _ is 30% of 20. 2 x/6=39/78 What is the value of x? 3 As an analyst for the Department of Natural Resources, you analyze samples of river water. A 2-liter sample of water contained about 24 of a particular organism and a 4-liter sample of water contained about 48 su

2、ch organisms. At this rate, how many of the organisms would you expect to find in a 10-liter sample of water from the same river? 4 If 20% of x equals 16, then x=_ 5 Jim scored 95 points in 5 basketball games for his school. At this rate, how many points will he have scored by the end of the 12-game

3、 season? GRE（ QUANTITATIVE）练习试卷 14答案与解析 1 【正确答案】 To solve this problem, set up a proportion. You are looking for a number that is 30% of 20. The proportion will be x/20=30/100. because the unknown number is 30% of the whole (20). To solve, cross-multiply, leaving you with 100x=600. Divide both sides

4、 by 100, and you get the final answer: x=6. 2 【正确答案】 You are given a proportion to solve. To find the answer, cross-multiply, giving you 78x=234. Dividing both sides by 78 will give you the answer: x=3. 3 【正确答案】 To answer this question you must determine the ratio of organisms to liters of river wat

5、er. The problem states that a 2-liter sample of water contained about 24 organisms and a 4-liter sample of water contained about 48 organisms. Upon closer examination of this information you will see that the ratio of organisms to water is the same in each sample. Therefore, you can set up a ratio u

6、sing one sample: 2 liters of water yields 24 organisms. This can be expressed as 2 to 24, or 2:24, which can be reduced to 1:12. For every 1 liter of water you will see 12 organisms. Therefore, 10 liters of water will contain 120 organisms. 4 【正确答案】 Set up a proportion. You are given that 20% of x i

7、s equal to 16, and you want to find the value of x. The proportion will look like this: 16/x=20/100 After cross-multiplying, you are left with 20x=1,600. After dividing both sides by 20, you have the answer: x=80. 5 【正确答案】 Use a proportion to solve this problem. You know that Jim scored 95 points in

8、 5 games, and you want to find out how many points he will score in a total of 12 games. The proportion will look like this: 95/5=x/12 Cross-multiply to get 5x = 1,140. Divide both sides by 5, and you get the answer: x=228. If Jim continues to score at this rate, he will score a total of 228 points by the end of the season (12 games).