Site Navigation
Site Directions
Search AlgebraLAB
Career Profiles
Reading Comprehension Passages
Practice Exercises
Science Graphs
StudyAids: Recipes
Word Problems
Project History
Project Team

Algebra II Recipe: Arithmetic Series
A. Definition
B. Finding the sum of the first n terms of an arithmetic sequence
  1. Use  is the sum of the first n terms.
  2. Write a rule for the nth term using the a1 and d values.
  3. Find the nth term by substituting the value of n into the rule.
  4. Substitute the n, a1, and an values into  to find the sum.
C. Finding n when Sn is known
  1. Substitute the sum for Sn.
  2. Substitute the first term for a1.
  3. Substitute the rule for an.
  4. Solve for n.
    • If you get a quadratic equation, solve by factoring or the quadratic formula.
    • Choose the positive value.

Consider the arithmetic series 4 + 7 + 10 + 13 + 16 + 19 + …
Find the sum of the first 30 terms (n = 30).

Consider the arithmetic series 4 + 7 + 10 + 13 + 16 + 19 + …
Find n when Sn = 175.

G Redden

Show Related AlgebraLab Documents

Return to STEM Sites AlgebraLAB
Project Manager
   Catharine H. Colwell
Application Programmers
   Jeremy R. Blawn
   Mark Acton
Copyright © 2003-2023
All rights reserved.