请问有GWD31的数学详解么？GWD31两道数学题

做得真崩溃，眼看题目这么简单，就是做不出来，真是工作久了害得。请问有GWD31的数学详解么？，有的话请告知链接，没的话，请帮我看看下面的两道题目。

GWD31-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 %

B.(k-m)%

C.[100(k-m)]/(100+k)%

D.[100(k-m)]/(100+m)%

E.[100(k-m)]/(100+k+m)%

答案：D

更崩溃的一题，我做了，五个选项中却没有我计算的答案

GWD31-Q14

How many seconds will it take for a car that is traveling at a constant rate of 45 miles per hour to travel a distance of 22 yards? (1 mile = 1,160 yards)

A. 8

B.9

C.10

D.11

E.12

答案： C

先多谢了，不要笑我蠢啊，才开始准备GMAT：（

真是太感谢你了，我以为我的智商已经低于70了 ：（

那第一题是怎么做的呢？

Let the original price/share = a ,
earning / share = b

Original ratio = a/b
New ratio = a(1 + k/100) / b(1+m/100) = a(100 + k ) /b(100+m)

Increase in ratio = New ratio - Original ratio = a(100 + k ) /b(100+m) - a/b = a(k-m)/b(100+m)
a(k-m)/b(100+m)/(a/b)...then times 100 to get the percent


Thus, Answer should be D