gmat数学题
问题描述：
gmat数学题
In a corporation,50 percent of the male employees and 40 percent of the female employees are at least 35 years old.If 42 percent of all the employees are at least 35 years old,what fraction of the employees in the corporation are females?
A.\x053/5
B.\x052/3
C.\x053/4
D.\x054/5
E.\x055/6
答
D
假设 男员工共有a人,女员工共有b人,
那么50%a+40%b=42%（a+b）
不妨设a+b=100,那么a=100-b
代入 50-50%b+40%b=42
10%b=8
b=4/5