8. A certain strain of S. pneumoniae is modeled by A(t) = A,ekt where Ao is the initial number of bacteria and t is the elapsed time, measured in minutes. Previous studies have established that the doubling time of this bacterium is 22 minutes. Suppose 1200 bacteria are initially present. (a) Find the growth constant k. Round your answer to four decimal places. AH = | 200 e A (33) = 7.37918 (b) Find a function which gives the number of bacteria A(t) after t minutes. (c) How long until there are 8500 bacteria? Round your answer to the nearest minute.

Calculus: Early Transcendentals
8th Edition
ISBN:9781285741550
Author:James Stewart
Publisher:James Stewart
Chapter1: Functions And Models
Section: Chapter Questions
Problem 1RCC: (a) What is a function? What are its domain and range? (b) What is the graph of a function? (c) How...
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# Exponential Growth Model of S. pneumoniae Bacteria

This problem involves modeling the growth of a strain of *S. pneumoniae* bacteria. The growth is described by the exponential function:

\[ A(t) = A_0 e^{kt} \]

- \( A_0 \) is the initial number of bacteria.
- \( t \) is the elapsed time in minutes.
- \( k \) is the growth constant.

## Given Data

- Initial bacteria count (\( A_0 \)): 1200
- Doubling time: 22 minutes

### (a) Finding the Growth Constant \( k \)

To find \( k \), we use the fact that the population doubles in 22 minutes.

Equation: \( A(22) = 2A_0 \)

Substituting in \( A(t) = A_0 e^{kt} \):

\[ 2 \times 1200 = 1200 \times e^{22k} \]

This simplifies to:

\[ 2 = e^{22k} \]

Solving for \( k \) gives:

\[ \ln(2) = 22k \implies k = \frac{\ln(2)}{22} \]

Thus, \( k \) is calculated and rounded to four decimal places.

### (b) Deriving the Function for \( A(t) \)

Substitute \( k \) back into the original equation \( A(t) = 1200 e^{kt} \) to find the function for the number of bacteria at any time \( t \).

### (c) Time Until Population Reaches 8500

To find the time it takes for the bacteria count to reach 8500, set up the equation:

\[ 8500 = 1200 e^{kt} \]

Solve for \( t \):

\[ \frac{8500}{1200} = e^{kt} \]

\[ \ln\left(\frac{8500}{1200}\right) = kt \]

\[ t = \frac{\ln\left(\frac{8500}{1200}\right)}{k} \]

Calculate the time \( t \) and round to the nearest minute.

### Diagram Details

There are handwritten calculations showing the setup for solving parts (a) through (c). The calculations follow the logical sequence of solving exponential growth problems, ensuring understanding of each step.

This educational explanation aims to help
Transcribed Image Text:# Exponential Growth Model of S. pneumoniae Bacteria This problem involves modeling the growth of a strain of *S. pneumoniae* bacteria. The growth is described by the exponential function: \[ A(t) = A_0 e^{kt} \] - \( A_0 \) is the initial number of bacteria. - \( t \) is the elapsed time in minutes. - \( k \) is the growth constant. ## Given Data - Initial bacteria count (\( A_0 \)): 1200 - Doubling time: 22 minutes ### (a) Finding the Growth Constant \( k \) To find \( k \), we use the fact that the population doubles in 22 minutes. Equation: \( A(22) = 2A_0 \) Substituting in \( A(t) = A_0 e^{kt} \): \[ 2 \times 1200 = 1200 \times e^{22k} \] This simplifies to: \[ 2 = e^{22k} \] Solving for \( k \) gives: \[ \ln(2) = 22k \implies k = \frac{\ln(2)}{22} \] Thus, \( k \) is calculated and rounded to four decimal places. ### (b) Deriving the Function for \( A(t) \) Substitute \( k \) back into the original equation \( A(t) = 1200 e^{kt} \) to find the function for the number of bacteria at any time \( t \). ### (c) Time Until Population Reaches 8500 To find the time it takes for the bacteria count to reach 8500, set up the equation: \[ 8500 = 1200 e^{kt} \] Solve for \( t \): \[ \frac{8500}{1200} = e^{kt} \] \[ \ln\left(\frac{8500}{1200}\right) = kt \] \[ t = \frac{\ln\left(\frac{8500}{1200}\right)}{k} \] Calculate the time \( t \) and round to the nearest minute. ### Diagram Details There are handwritten calculations showing the setup for solving parts (a) through (c). The calculations follow the logical sequence of solving exponential growth problems, ensuring understanding of each step. This educational explanation aims to help
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