Gauss's Trick for Adding 1+2+...+100
Explore the visual representation of finding the sums:
1
1+2
1+2+3
1+2+3+4
...
1+2+3+4+5+6+7+8+9+10
Or, in other words, finding the first 10 partial sums of the arithmetic sequence
Write a formula for each partial sum, and generalize this to the partial sum.