Question

Work out: 1 - 2 + 3 - 4 + 5 - 6 + 7 - 8 + ...... + 1599 - 1600

I congratulate you if you manage to solve it!!!

Answer 1

`1-2+3-4+5-6+7-8+1599-1600`

Add and subtract from left to right.


`1-2=-1 \ \textgreater \ -1+3-4+5-6+7-8+1599-1600 \ \textgreater \ -1+3=2`


`2-4+5-6+7-8+1599-1600 \ \textgreater \ 2-4=-2`


`-2+5-6+7-8+1599-1600 \ \textgreater \ -2+5=3`


`3-6+7-8+1599-1600 \ \textgreater \ 3-6=-3`


`-3+7-8+1599-1600 \ \textgreater \ -3+7=4`


`4-8+1599-1600 \ \textgreater \ 4-8=-4 \ \textgreater \ -4+1599-1600`


`-4+1599=1595 \ \textgreater \ 1595-1600 \ \textgreater \ 1595-1600=-5`

Therefore our answer is -5.

Hope this helps!