Elementary and Intermediate Algebra: Concepts & Applications (6th Edition)

Published by Pearson
ISBN 10: 0-32184-874-8
ISBN 13: 978-0-32184-874-1

Chapter 14 - Sequences, Series, and the Binomial Theorem - 14.3 Geometric Sequences and Series - 14.3 Exercise Set - Page 912: 54

Answer

Yes, the given infinite geometric series has a limit, and the value of the limit is ${{S}_{\infty }}=\$12,500$.

Work Step by Step

$\$1000{{\left(1.08\right)}^{-1}}+\$1000{{\left(1.08\right)}^{-2}}+\$1000{{\left(1.08\right)}^{-3}}+\cdots$ Here ${{a}_{1}}=\$1000{{\left(1.08\right)}^{-1}},{{a}_{2}}=\$1000{{\left(1.08\right)}^{-2}}$ $\begin{align} & \left| r \right|=\left| \frac{{{a}_{2}}}{{{a}_{1}}} \right| \\ & =\left| \frac{\$1000{{\left(1.08\right)}^{-2}}}{\$1000{{\left(1.08\right)}^{-1}}}\right|\\&=\left|{{\left(1.08\right)}^{-1}}\right|\\&={{\left(1.08\right)}^{-1}}\end{align}$ Find the limit of the infinite geometric series using the formula ${{S}_{\infty }}=\frac{{{a}_{1}}}{1-r}$. $\begin{align} & {{S}_{\infty }}=\frac{{{a}_{1}}}{1-r} \\ & =\frac{\$1000{{\left(1.08\right)}^{-1}}}{1-{{\left(1.08\right)}^{-1}}}\\&=\frac{\frac{\$1000}{\left(1.08\right)}}{1-\left(\frac{1}{1.08}\right)}\\&=\frac{\frac{\$1000}{1.08}}{\frac{0.08}{1.08}}\end{align}$ This implies that, $\begin{align} & {{S}_{\infty }}=\frac{\$1000}{1.08}\cdot\frac{1.08}{0.08}\\&=\frac{\$1000}{0.08}\\&=\$12,500\end{align}$ Thus, the limit of the infinite geometric series is ${{S}_{\infty }}=\$12,500$.
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