## Algebra and Trigonometry 10th Edition

$0.412$
We need to use an exponential decay model such as: $y= q( \dfrac{1}{2})^{t/24100}$ or, $q=\dfrac{y}{( \dfrac{1}{2})^{t/24100}}$ or, $q= y \times ( \dfrac{1}{2})^{-t/24100}$ The initial quantity after $1000$ years is: $q= 0.4 \times ( \dfrac{1}{2})^{-1000/24100} \approx 0.412$