# Chapter 7 Exponential and Logarithmic Functions - 7.6 Solve Exponential and Logarithmic Equations - 7.6 Exercises - Problem Solving - Page 521: 57

$\approx6967$

#### Work Step by Step

Plugging in $R=5$ into the given formula: $5=100e^{-0.00043t}\\0.05=e^{-0.00043t}\\\ln0.05=-0.00043t\\t=\frac{\ln0.05}{-0.00043}\approx6967$

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