Question

1+2+3+4+5+6+7+.....+998+999+1000+1001+1002

Answer 1

[tex]1+2+3+4+....+1002=\\ \frac{1002*1003}{2}=501*1003=502503 [/tex]

Answer 2

$\displaystyle 1+2+3+4+5+6+7+...+998+999+1000+1001+1002= \\ \\ = \frac{1002(1002+1)}{2} = \frac{1002 \cdot 1003}{2} = \frac{1005006}{2} =502503$