In a corporation, 50% of the male employees and 40% of the female employees

are at least 35 years old. If 42% of all the employees are at least 35 years old,

what fraction of the employees in the comporation are females?

a.3/5 b.2/3 c.3/4 d.4/5 e.5/6

請給個思路,謝謝.

total X , femal Y

(X-Y)*50% + Y * 40% = X * 42%

then Y/X = ?

0.5x-0.5y+0.4y=0.42x

0.08x=0.1y

y/x = 0.08/0.1 = 0.8 = 4/5