### Home > PC3 > Chapter 13 > Lesson 13.1.1 > Problem13-10

13-10.

What is the sum of the first $20$ terms of the series $100−20+90−18+$$80−16+\dots$? Describe your technique. Can you find a method where you do not have to add up each of the terms individually?

One method is to make this into two different series, each with $10$ terms.