Question 1209331
.


This problem admits simple mathematical mental solution.


Group the terms in pairs


1-2+3-4+5-6+.....+2007-2008+2009-2010+2011 = (1-2)+(3-4)+(5-6)+.....+(2007-2008)+(2009-2010)+2011.



You have 2010/2 = 1005 pairs and the last unpaired term 2011.


Each pair produces -1, so the total expression is -1005+2011, and you can calculate it mentally.



<U>ANSWER</U>.  &nbsp;&nbsp;1006.



Solved &nbsp;(mentally)



This problem is specially designed to be solved in this way.