※ 引述《domeself (be strong)》之铭言： : 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 : ANS:C : Thanks. 第一次在gmat板上po文 我试解一下 不知道说不说得清楚 原题意为 有接种过Rubella(德国麻疹)疫苗的小孩数目是有接种过Mumps(腮腺炎)的小孩数目的两倍 将代数式设为 R=2M 另外，题又说 两种疫苗都有接种过的小孩数目是只接种过mumps小孩数的两倍 将两种疫苗都有接种过的小孩数目设为X 则此句话的代数式为 X=2(M-X) 题目并告诉我们 两种疫苗都有接种过的小孩数目为5000 将5000代入第二式X中 可求出M=7500 再将M=7500代入一式中 可求出R=15000 但最後要小心 题目问的是只接种过Rubella疫苗小孩的数量 所以还要将R-X=15000-5000=10000 才是答案喔!! --

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