Question

what is the sum of the numbers 1 to 1000?

ans:500500

Answer 1

start at 499, 501 the sum is 1000
then 498,502 the sum is 1000
do that a total of 50 times, or 50000total, then add the center number, 500 to sum
50500

Now here is another way:
pair the numbers, first to last:
1+1000=1001
2+999= 1001
do that till you have to 500times, sum is 50500

Now if you want a formula for the sum of N numbers.... (N+1)(N/2)

Answer 2

THANKS I JUST WANTED TO MAKE SURE