What is the value of $$1+3+5+\cdots +2017+2019-2-4-6-\cdots -2016-2018$$? 
Overseas Competition->Knowledge Point->Calculation Modules->Whole Numbers->Whole Numbers Addition and Subtraction ->Grouping in Fast Addition and Subtraction of Whole Numbers
Solution 1  Rearranging the terms, we get $$(1-2)+(3-4)+(5-6)+\cdots (2017-2018)+2019$$, and our answer is $$-1009+2019=1010$$.  Solution 2  We can rewrite the given expression as  $$1+(3-2)+(5-4)+\cdots +(2017-2016)+(2019-2018)=1+1+1+\cdots +1$$. The number of $$1$$s is the same as the number of terms in $$1$$, $$3$$, $$5$$, $$7\cdots $$, $$2017$$, $$2019$$. Thus the answer is $$1010$$. 