Precalculus: Mathematics for Calculus, 7th Edition

Published by Brooks Cole
ISBN 10: 1305071751
ISBN 13: 978-1-30507-175-9

Chapter 4 - Section 4.1 - Exponential Functions - 4.1 Exercises - Page 337: 59

Answer

a) 519.02 dollars b) 538.75 dollars c) 726.23 dollars

Work Step by Step

First one has to find the function that models the example. This uses the compound interest function $A(t)=P\left(1+\frac{r}{n}\right)^{nt}$, where $P$ is the principal value, $r$ is the interest rate per year, $n$ is the number of times the interest is compounded per year, and $t$ is the number of years. The principal $p$ is \$500 dollars, the interest rate $r$ is 3.75% or 0.0375 in decimal form, and the number of times it is compounded annually $n$ is 4. Now the function can be described: $A(t)=500\cdot \left(1+\frac{0.0375}{4}\right)^{4t}$ Now one only needs to calculate $A(1)$, $A(2)$, and $A(10)$ which corresponds to the investment after 1, 2, and 10 years, respectively. $A(1)=500\cdot \left(1.009375\right)^{4(1)}=$ $500\cdot (1.009375)^{4}=519.02$ dollars $A(2)=500\cdot \left(1.009375\right)^{4(2)}=$ $500\cdot (1.009375)^{8}=538.75$ dollars $A(10)=500\cdot \left(1.009375\right)^{4(10)}=$ $500\cdot (1.009375)^{40}=726.23$ dollars
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