13.
Consider the infinite geometric series \(\displaystyle \frac{1}{5}+\frac{1}{10}+\frac{1}{20}+\frac{1}{40}+\frac{1}{80}+\ldots\).
How do you graphically and algebraically explain to students what happens to \(S_n\) as \(n\) increases?

111.6.25補充
以下的圖出自
Proofs without Words: Exercises in Visual Thinking (Classroom Resource Materials) First Edition, Later Printing
https://www.amazon.com/Proofs-wi ... sroom/dp/0883857006