GWD题目一道~~~~是否答案有误？

白菜白菜

Q19:

In a certain region, the number of children who have been vaccinated against rubella is twice the number who have been vaccinated against mumps.  The number who have been vaccinated against both is twice the number who have been vaccinated only against mumps.  If 5,000 have been vaccinated against both, how many have been vaccinated only against rubella?

A. 2,500
B. 7,500
C. 10,000
D. 15,000
E. 17,500




答案是C 怎么算都是A啊 是答案错了咩？

白菜白菜

啊啊=。=刚才又仔细看了一遍，是10000没错。。。是自己粗心了~

琪琪baby

答案应该是C，我还没有开始准备GMAT。但是从数学的角度来看，我算出来的是10000.
你可以设only against mumps的为x，only against rubella的为y，both的为z。
有2（x+z）=y+z和z=2x,再把z=5000代入得到y=10000.
这是我的想法，你看看对不对！

白菜白菜

嗯嗯 正是~~谢谢啦~