Add the first number in the sequence to the last number in the sequence. Multiply that sum by the number of numbers in the sequence. Divide that product by 2.
Hint: This is a series of sequential numbers, so the number of numbers is the largest number minus the smallest number then add 1. Example: How many numbers from 1 to 10? 10 minus 1 plus 1 = 10. How many from 10 to 20? 20 minus 10 plus 1 = 11.
John
My calculator said it, I believe it, that settles it
