Question

What is the sum of the first 39 positive odd numbers?

Answer 1

1-39 ODD:
1,3,5,7,9,11,13,15,17,19,21,23,25,27,29,31,33,35,37,39
Now you'd add them all up.
1+3+5+7+9 = 25
11+13+15+17+19 = 75
21+23+25+27+29 = 125
31+33+35+37+39 = 175
Add the totals:
25+75+125+175
The answer would be 400.