Answer:
Step-by-step explanation:
Gauss n(n+1)/2
which is n? the last number of the sum
500(500 + 1)/2 = 125,250
800(800+1)/2 = 320,400
uh oh forgot to read the last one, give me a minute. done
(800 - 501 + 1)(800 + 501)/2
300(1301)/2 = 195,150
or
320,400 - 125,250 = 195,150
