这道题目为什么是这样？

sinadragon

Q18:

Last year the price per share of Stock X increased by k percent and the earnings per share of Stock X increased by m percent, where k is greater than m.  By what percent did the ratio of price per share to earnings per share increase, in terms of k and m?

 A.     k/m %

 A.     k/m %

B.     (k-m) %

C.     [100(k-m)]/(100+k) %

D.     [100(k-m)]/(100+m) %

E.      [100(k-m)]/(100+k+m) %

Answer: 为什么是D，哪一位帮忙看一下，TT里面没有说明

sinadragon

谢谢，明白了。

cherrywds

设原来的price为A，原来的earning为B，则原来的ratio为A/B，增长后的ratio为（100+k）A/（100+m）B。求增长率可得D。