Thinking Mathematically (6th Edition)

Published by Pearson
ISBN 10: 0321867327
ISBN 13: 978-0-32186-732-2

Chapter 8 - Personal Finance - 8.4 Compound Interest - Exercise Set 8.4 - Page 521: 30

Answer

5.25%

Work Step by Step

In order to compute the effective annual yield when interest is compounded monthly following formula can be used where Y is the effective yield, r is the rate that is 5% and n is compounding period. The interest is compounded monthly therefore n (compounding period) is taken as 12. By using formula \[\begin{align} & Y={{\left( 1+\frac{r}{n} \right)}^{n}}-1 \\ & ={{\left( 1+\frac{0.05}{12} \right)}^{12}}-1 \\ & ={{\left( 1+0.004167 \right)}^{12}}-1 \end{align}\] \[\begin{align} & ={{\left( 1.004167 \right)}^{12}}-1 \\ & =1.0512-1 \\ & =0.0512\text{or5}\text{.12}percent \end{align}\] Now computing effective annual yield when rate of interest is 5.25% The interest is compounded quarterly therefore, n (compounding period) is taken as 4. \[\begin{align} & Y={{\left( 1+\frac{r}{n} \right)}^{n}}-1 \\ & ={{\left( 1+\frac{0.0525}{4} \right)}^{4}}-1 \\ & ={{\left( 1+0.013125 \right)}^{4}}-1 \end{align}\] \[\begin{align} & ={{\left( 1.013125 \right)}^{4}}-1 \\ & =1.0535-1 \\ & =0.0535or5.35percent \end{align}\] Thus, 5.25% compounded quarterly is the better investment.
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