GWD数学一道简单的小题。求助！

kenshins

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.3/5
B.2/3
C.3/4
D.4/5
E.5/6

avalon9527

设有男雇员x人，女雇员y人。则共有雇员x+y人，其中0.5x+0.4y都是35岁以上的员工。即0.5x+0.4y=0.42(x+y)
求出y/(x+y)=4/5

youngerlee

male employees为x， female为y
列等式
50%*x+40%*y=42%(x+y）
比例应该能做出来

kenshins

这个等式我列过，可是没算出来，LS能给出详细算法么?

fabiana

答案是不是D?只设女雇员的占比为X，所以男雇员的占比为(1－X)

0.5*（1-X）＋0.4*X=0.42

可以计算出X＝0.8

fabiana

回复 4# kenshins


   

答案是不是D?只设女雇员的占比为X，所以男雇员的占比为(1－X) 0.5*（1-X）＋0.4*X=0.42 可以计算出X＝0.8