Differential Equations and Linear Algebra (4th Edition)

Published by Pearson
ISBN 10: 0-32196-467-5
ISBN 13: 978-0-32196-467-0

Chapter 1 - First-Order Differential Equations - 1.5 Some Simple Population Models - Problems - Page 51: 2

Answer

Thus, the initial size of the culture is $2032$ and the doubling time of the population is $7.701$

Work Step by Step

Given that: $P(t)=P_0e^{(kt)}$ Doubling the time: $t_d=\frac{1}{k} \ln 2$ We know that after 10 hours, there were 5000 bacteria present. $5000=P_0e^{(10k)}$ And after 12 hours, there were 6000 bacteria present. $6000=P_0e^{(12k)}$ To find $k$ $\frac{5000}{6000}=\frac{P_0e^{(10k)}}{P_0e^{(12k)}}$ $e^{-2k}=\frac{5}{6}$ $-2k=\ln(\frac{5}{6})$ $k \approx 0.09$ So, $5000=P_0e^{(10\times 0.09)}$ $P_0 \approx 2032$ And the doubling time of the population: $t_d=\frac{1}{0.09} \ln 2$ $t_d \approx7.701$ Thus, the initial size of the culture is $2032$ and the doubling time of the population is $7.701$ hours.
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