Algebra 2 Common Core

Published by Prentice Hall
ISBN 10: 0133186024
ISBN 13: 978-0-13318-602-4

Chapter 9 - Sequences and Series - Chapter Review - Page 606: 45

Answer

$S = 187.5$

Work Step by Step

To determine whether or not this series converges or diverges, we need to find the common ratio, $r$. This can be done by setting up a ratio of the second term to the first term: $r = \frac{30}{150} = \frac{1}{5}$ When $|r| \lt 1$, then the series converges; when $|r| \gt 1$, then the series diverges. Since $|r| \lt 1$ in this case, this series converges. To find the sum of this convergent geometric series, we can use the formula: $S_n = \frac{a_1(1 - r^n)}{1 - r}$, $r \ne 1$, where $S_n$ is the sum of the series, $n$ is the number of terms in the series, $a_1$ is the first term, and $r$ is the common ratio. We already have $a_1 = 150$, $n = \frac{1}{5}$, and $r = \frac{1}{5}$. We can now use the following formula to calculate the sum of a convergent geometric series: $S = \frac{a_1}{1 - r}$ Plug in our known values: $S = \frac{150}{1 - \frac{1}{5}}$ Subtract first: $S = \frac{150}{\frac{4}{5}}$ Divide fractions by multiplying the numerator by the reciprocal of the denominator: $S = \frac{150}{1} \times \frac{5}{4}$ Multiply: $S = \frac{750}{4}$ Simplify: $S = 187.5$
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