题目

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.x0510,100
B.x0520,200
C.x0522,650
D.x0540,200
E.x0545,150
C.x0522,650

提问时间：2020-08-03

答案

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……