Respuesta :
Answer:
A) The initial size o the culture is 640
B) The doubling period is 47 minutes
C) The population after 60 minutes is 1563
D) The population will reach 13000 after 3 hours 22 minutes
Explanation:
The form of an exponential grow model is:
[tex]S=Pb^t[/tex]Where:
S is the population after t hours
P is the initial population
b is the base of the exponent
t is the time, in hours
We know that after 15 minutes, the population was 800. 15 minutes is a quarter of an hour. Thus, t = 1/4, S = 800:
[tex]800=Pb^{\frac{1}{4}}[/tex]Also, we know that after 30 minutes, the population was 1000. Thus, t = 1/2, S = 1000
[tex]1000=Pb^{\frac{1}{2}}[/tex]Then, we have a system of equations:
[tex]\begin{cases}800=Pb^{\frac{1}{4}}{} \\ 1000=Pb^{\frac{1}{2}}{}\end{cases}[/tex]We can solve the first equation for P:
[tex]\begin{gathered} 800=Pb^{\frac{1}{4}} \\ P=\frac{800}{b^{\frac{1}{4}}} \end{gathered}[/tex]And substitute in the other equation:
[tex]1000=\frac{800}{b^{\frac{1}{4}}}b^{\frac{1}{2}}[/tex]And solve:
[tex]\frac{1000}{800}=\frac{b^{\frac{1}{2}}}{b^{\frac{1}{4}}}[/tex][tex]\begin{gathered} \frac{5}{4}=b^{\frac{1}{2}-\frac{1}{4}} \\ . \\ \frac{5}{4}=b^{\frac{1}{4}} \end{gathered}[/tex][tex]\begin{gathered} b=(\frac{5}{4})^4 \\ . \\ b=\frac{625}{256} \end{gathered}[/tex]Now, we can find the initial population P:
[tex]P=\frac{800}{(\frac{625}{256})^4}=\frac{800}{\frac{5}{4}}=\frac{800\cdot4}{5}=640[/tex]The initial population is 640
To find the doubling period, we want that the population equal to twice the initial population:
[tex]S=2P[/tex]Then, since we know the equation, we can write:
[tex]2P=P(\frac{625}{256})^t[/tex]Then:
[tex]\begin{gathered} \frac{2P}{P}=(\frac{625}{256})^t \\ . \\ 2=(\frac{625}{256})^t \\ \ln(2)=t\ln(\frac{625}{256}) \\ . \\ \frac{\ln(2)}{\ln(\frac{625}{256})}=t \\ . \\ t\approx0.7765 \end{gathered}[/tex]If an hour is 60 minutes:
[tex]60\cdot0.7765=46.59\approx47\text{ }minutes[/tex]To find the population after 60 minutes, we use t = 1 hour and we want to find S:
[tex]\begin{gathered} S=640(\frac{625}{256})^1 \\ . \\ S=640\cdot\frac{625}{256}=1562.5 \end{gathered}[/tex]To find when the population is 13000, then we use S = 13000 and solve for t:
[tex]\begin{gathered} 13000=640(\frac{625}{256})^t \\ . \\ \frac{13000}{640}=(\frac{625}{256})^t \\ . \\ \frac{325}{16}=(\frac{625}{256})^t \\ . \\ \ln(\frac{325}{16})=t\ln(\frac{625}{256})^ \\ . \\ t=\frac{\ln(\frac{325}{16})}{\ln(\frac{625}{256})}\approx3.373 \\ \\ \end{gathered}[/tex]We have 3 full hours and 0.373. Since one hour is 60 minutes:
[tex]60\cdot0.373\approx22[/tex]The population reach 13000 after 3 hours 22 minutes
