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　　GRE数学混合物问题介绍

　　In mixture problems, you combine substances with different characteristics, resulting in a particular mixture or proportion. Here are some typical scenarios:

　　Wet Mixtures involving liquids，gases，or granules，which are measured and mixed by volume or weight, not by number (quantity).

　　Dry Mixtures involving a number of discreet objects，such as coins, coolies, or marbles, that are measured and mixed by number (quantity) as well as by relative weight, size, value, and so on.

　　溶液混和问题通常要涉及浓度和百分比，而固态物质相混和的问题则通常涉及到原始数目和数量。但是不管是溶液混合还是固态物质混合，解决它们的思路都是一样的，既要牢牢抓住混合前后的不变量。

　　GRE数学混合物问题实例讲解

　　1. How many quarts of pure alcohol must you add to 15 quarts of solution that is 40 % alcohol to strengthen it to a solution that is 50% alcohol?

　　解：The original amount of alcohol is 40 % of 15. Letting x equal the number of quarts of alcohol that you must add to achieve a 50% alcohol solution, 0. 4 X 15 + x equals the amount of alcohol in the solution after adding more alcohol. You can express this amount as 50% of (15 + x). Thus, you can express the mixture algebraically as follows： 0.4X15 + a: = 0. 5(15 + x)，x = 3 You must add three quarts of alcohol to achieve a 50% alcohol solution.

　　2. Brand R coffee costs $3. 25 per pound and brand T coffee costs $ 2. 50 per pound.

　　A The number of pounds of brand R in a mixture of brands R and T that costs $ 3. 00 per pound

　　B 1.2

　　R 牌咖啡每镑$3. 25,T 牌咖啡每镑$2. 50。

　　解：本题的正确答案为(D)。比较的左项为R与T混合后每镑值$ 3. 00的咖啡中R牌咖啡的镑数。设R和T各有x和y镑，根据题意列出方程：

　　3. 25x + 2. 50y = 3. 00 (x+y)， x = 2y 显然，我们只能得到R和T两种牌子的咖啡在混和咖啡中所占的比例，若要求出R牌咖啡的确切重量，还必须给出混和咖啡的总重量或者T牌咖啡的重量。

　　以上就是小编为大家带来的GRE数学混合物问题，同学们如果还有任何关于出国留学的问题，可以拨打一诺留学的免费热线400-003-6508或者010-62680991进行咨询，或者点击一诺留学官方网站http://www.yinuoedu.net/页面的“在线咨询”与一诺留学专家直接对话。微信订阅号：留学圈 (微信帐号：yinuoliuxue )