## Precalculus (6th Edition) Blitzer

Published by Pearson

# Chapter 3 - Test - Page 515: 24

#### Answer

$13.9$ years

#### Work Step by Step

The formula for compound interest wit $n$ compoundings per year is given by : $A= P(1+\dfrac{r}{n} )^{nt}$ Plug in the given data. $8000=4000 (1+\dfrac{0.05}{4} )^{4t}$ or, $2=(1.0125)^{4t}$ Take the log of each side. $t= \dfrac{\ln 2}{4 \ln 1.0125} \approx 13.9$ years

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