Chapter 5 - Exponential and Logarithmic Functions - 5.4 Logarithmic Functions - 5.4 Assess Your Understanding - Page 297: 126

$3.98$

We know that $N=P(1-e^{-0.15d})$, hence if $N=450$ and $P=1000$, then: $450=1000(1-e^{-0.15d})\\\frac{450}{1000}=1-e^{-0.15d}\\0.45=1-e^{-0.15d}\\-0.55=-e^{-0.15d}\\0.55=e^{-0.15d}\\\ln {{0.55}}=-0.15d\\d=\frac{\ln {{0.55}}}{-0.15}\approx3.98$