# Proof without Words: $$\sum ar^n = a/(1-r)$$

by J. H. Webb

This article originally appeared in:
Mathematics Magazine
June, 1987

Subject classification(s): Sequences and Series | Geometric Sequence
Applicable Course(s): 2.1 College Algebra | 2.3 College Algebra & Trigonometry combined | 3.1 Mainstream Calculus I

The author presents a geometric proof for the sum of a geometric series by using similar triangles.

A pdf copy of the article can be viewed by clicking below. Since the copy is a faithful reproduction of the actual journal pages, the article may not begin at the top of the first page.

To open this file please click here.

These pdf files are furnished by JSTOR.

Classroom Capsules would not be possible without the contribution of JSTOR.

JSTOR provides online access to pdf copies of 512 journals, including all three print journals of the Mathematical Association of America: The American Mathematical Monthly, College Mathematics Journal, and Mathematics Magazine. We are grateful for JSTOR's cooperation in providing the pdf pages that we are using for Classroom Capsules.