GWD-01-28,求思路，多谢

Q28:

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

以100为首项,300为末项,公差(是这个术语吧)为2的等差数列求和.

300=100+N(N-1)2  N=101

SUM=N100+N(N-1)2/2=20200

选B.