Question

求一道Gmat数学题～谢谢 希望能解答详细过程

For any positive integer n, the sum of the first n positive integers equals [n(n+1)]/2. What is the sum of all the even integers between 99 and 301?
A. 10,100
B. 20,200
C. 22,650
D. 40,200
E. 45,150

答案：C. 22,650

Answer 1

求翻译！

1~99的和为99*（99+1）/2=4950
1~301的和为301*（301+1）/2=45451
100~301的和为45451-4950=40501
100~301 设偶数和为x 则奇数和为x+101 （共202个数，奇数和偶数各101个 奇数和比偶数和大101）
x+(x+101)=40501
x=20200
即偶数和为20200

貌似你的答案有问题饿……