Forgot Compounding Formula

Question

What's the formula for finding the sum of a range of numbers that increase 1 integer and continues example - starting at 20 through 60 what's the total of the numbers added ie. 20+21+22+23.....+60

Answer 1

Remember the young boy who grew up to be a great mathematician, Fredrick Gauss.

he took the numbers & added them in reverse, like this

20 21 22 23 24 .............55 56 57 58 59 60. Then add in reverse like so

60 59 58 57 56 .............25 24 23 22 21 20. No add the columns

80 80 80 80 80 .............80 80 80 80 80 80. There are 41 of the number 80 = 3280

now divide by 2 to get 1640 !