Question

1+2+3+4+....+999 =

Answer 1

1000*1000/2 = 500000

Answer 2

wait dammit

1000*999/2 = 499500

Answer 3

999*1000/2

Answer 4

1+2+3+4+...........+N =N(N+1)/2

Answer 5

\[\sum _{n=1}^{999} n=499500 \]

Answer 6

1+2+3+. . . +n
n+. . . +3+2+1
(n(n+1)) / 2

Answer 7

@kdrkitty
Did you understand it? :)

Answer 8

1+2+3+...+999
999+998+...+2+1

and now add the elements vertically. This will yield

1000+1000+1000+.....+1000,

which is just 999*1000 = 999000
Now this is twice the answer we wanted, so just divide by 2. The answer is 499500