Simple Bacteria doubling problem

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Homework Help Overview

The problem involves a bacterial population that doubles every 20 minutes, with a known population size at a specific time. The participants are exploring the mathematical model for population growth using the formula p(t)=A e^{kt} and attempting to determine the growth constant k, the initial population A, and the population size after 3 hours.

Discussion Character

  • Exploratory, Mathematical reasoning, Assumption checking

Approaches and Questions Raised

  • Participants discuss the relationship between the doubling time and the population growth formula, with attempts to derive k from the doubling period. Questions arise regarding the cancellation of variables and the implications for finding the initial population A.

Discussion Status

The discussion is active, with participants providing insights and corrections to each other's reasoning. Some have suggested methods to find k and A, while others express uncertainty about the implications of the variables involved. There is no explicit consensus yet on the correct values.

Contextual Notes

Participants are working under the constraints of a homework assignment, which may impose specific rules or expectations regarding the use of variables and the derivation of solutions.

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Homework Statement



The doubling period of a baterial population is 20 minutes. At time t = 120 minutes, the baterial population was 80000. With t representing minutes, the formula for the population is p(t)=A e^{kt}.

k=?
The initial population at time t = 0 is:?
The size of the baterial population after 3 hours is: ?



I attempted this problem and came up with k being (ln(2))/140. The online assignment keeps saying that is the wrong answer. If i can't find k, I can't get anything else. Please help me out.
 
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If the doubling time is twenty minutes then the population at time t=20 is twice the population at t=0. So 2*A*e^(k*0)=A*e^(k*20). Can you solve that for k? Notice the A cancels.
 
I am not sure. I can't solve that for k. I don't have A.
 
A cancels!
 
oh wow silly me. sorry. it does cancel
 
i got (ln(2))/20. Now how do i find t=0 if i don't know what A is.
 
Good start! You know 80000=A*e^(k*120). Can't you find A from that?
 

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