# Chapter 5 - 5.5 - Exponential and Logarithmic Models - 5.5 Exercises - Page 405: 23

$2.258$

#### Work Step by Step

We need to use an exponential decay model such as: $y= q( \dfrac{1}{2})^{t/5715}$ or, $q=\dfrac{y}{( \dfrac{1}{2})^{t/5715}}$ or, $q= y \times ( \dfrac{1}{2})^{-t/5715}$ The amount after $1000$ years is: $q= 2 \times ( \dfrac{1}{2})^{-1000/5715} \approx 2.258$

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