# Chapter 12 Sequences and Series - Mixed Review of Problem Solving - Lessons 12.1-12.3 - Page 818: 2c

When the number of rings is doubled, the total area is quadrupled. Please see the answer below.

#### Work Step by Step

From part (b), we have $a_i=(2i-1) \pi$ and $a_n=\sum_{i=1}^n (2i-1) \pi$ For $n=1; a_1=\sum_{i=1}^1 (2i-1) \pi=\pi$ For $n=2; a_2=\sum_{i=1}^2 (2i-1) \pi=\pi+3 \pi=4 \pi$ For $n=4; a_4=\sum_{i=1}^4 (2i-1) \pi=\pi+3 \pi+5 \pi+7 \pi=16 \pi$ For $n=8; a_8=\sum_{i=1}^8 (2i-1) \pi=\pi+3 \pi+5 \pi+7 \pi+9 \pi+11 \pi+13 \pi+15 \pi=64 \pi$ When the number of rings is doubled, the total area is quadrupled.

After you claim an answer you’ll have 24 hours to send in a draft. An editor will review the submission and either publish your submission or provide feedback.