# Chapter 7 Exponential and Logarithmic Functions - 7.1 Graph Exponential Growth Functions - 7.1 Exercises - Problem Solving - Page 485: 44a

$11.6\%$

#### Work Step by Step

Let $x$ be the number of years passed since the cost yearly was $5200$. Then our initial amount is $5200$, and the percent increase is: $r$. Then the cost after five years is: $5200(1+r)^5=9000\\(1+r)^5=\frac{9000}{5200}=\frac{45}{26}\\1+r=\sqrt[5] {\frac{45}{26}}\\r=\sqrt[5] {\frac{45}{26}}-1\approx0.116=11.6\%$

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