250500 … There are 501 even numbers if one starts with zero and ends with 1000. A quick way to determine their sum is to make 501 addition problems starting with 1000 + 0 … 998 + 2 … 996 + 4 … 994 + 6 … etc. all the way to 0 + 1000. read more
Until you have added the last pair, 498 and 502. (Don't forget 500, the only unpaired one). Each pair you put on adds another 1000. read more