问题
单项选择题
Seed mixture X is 40 percent ryegrass and 60 percent bluegrass by weight; seed mixture Y is 25 percent ryegrass and 75 percent fescue. If a mixture of X and Y contains 30 percent ryegrass, what percent of the weight of this mixture is X ？（）
A.A
B.B
C.C
D.D
E.E
答案
参考答案：B
解析：
设该混和种子中含X的重量百分比是x，则含Y的重量百分比是1-x，根据题意可得
。