正确答案: B

　　GMAT数学题目解析

　　读题目可以得到这样一个等式(0.4X+0.25y)/(x+y) =0.3，根据等式算出来x=2y，答案问的是x在XY混合物中的比例，三分之一，第二个答案。

　　The Methord bellow is realy too complicated。

　　————————————————————————————————————————————————————————

　　METHOD 1:

　　Assuming the weight of the mixture to be 100g**, then the weight of ryegrass in the mixture would be 30g.

　　Also, assume the weight mixture X used in the mixture is Xg, then the weight of mixture Y used in the mixture would be (100-X)g.

　　So we can now equate the parts of the ryegrass in the mixture as:

　　0.4X + 0.25(100-X) = 30

　　0.4X + 25 - 0.25X = 30

　　0.15X = 5

　　X = 5/0.15 = 500/15 = 100/3

　　So the weight of mixture X as a percentage of the weight of the mixture

　　= (weight of X/weight of mixture) * 100%

　　= (100/3)/100 * 100%

　　= 33%

　　METHOD 2

　　wt. of 1st mixture = x

　　therefore concentration of ryegrass in 1st mix = 0.4x

       以上就是本文的全部内容，更多精彩请随时关注新东方长春学校官网。

相关推荐

新东方GMAT全程班

长春新东方留学直通车