求解一道GMAT题!

题目

求解一道GMAT题!
forty percent of the rats included in an experiment were male rats.If some of the rats died during the experiment and 30 percent of the rats that died were male rats,what was the ratio of the death rate among the male rats to the death rate among the female rats?
A,9/14
B.3/4
C.9/11
D.6/7
E.7/8

答案

假设有100只老鼠被用来做实验,那么40只是公的,60只是母的.实验过程中假设死了10只,那么3只是公的,7只是母的.题目问：公的死亡率和母的死亡率之比是多少?
=3/40:7/60
=180:280
=9:14
所以正确的是A.9/14