Here we will consider the following simplified version of the model: dS dt = -aS IP %3D aS – bI dt dR dt bI where the functions S(t), I(t), R(t) and the constants a, b > 0 represent: S(t) = the percentage of the population that is susceptible (i.e., has not contracted the disease) I(t) the percentage of the population that is infected (i.e., contagious) R(t) the percentage of the population that is recovered (i.e., no longer contagious) = the constant infection rate a = the constant rate of recovery (a) Solve the differential equation -aS. (b) Substitute your answer from (a) into the differential equation 4 = aS – bI and then solve for I. dR (c) Substitute your answer from (b) into the differential equation bI and then solve for R. (d) Identify the general solution to the simplified SIR model in (2). (e) Suppose there is an outbreak of malaria in Central America. If the typical rate of recovery for malaria is b = 2 and preliminary studies estimate the infection rate is between 0.03 < a < 0.07, plot the graphs of S(t), I(t), R(t) on the same axes. State the value of a that you used. (f) Compare the graphs of S(t), I(t), R(t) for several values of a. Describe in words how does the a-value affect your solutions?

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Chapter2: Second-order Linear Odes
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Ordinary Partial diff. eqn. 

I need help with question 4. a,b,c,d,e and f

Here we will consider the following simplified version of the model:
dS – -aS
dt
dI
dt
aS – bI
(2)
dR
dt
where the functions S(t), I(t), R(t) and the constants a, b > 0 represent:
S(t)
the percentage of the population that is susceptible (i.e., has not contracted the disease)
I(t)
the percentage of the population that is infected (i.e., contagious)
R(t)
the percentage of the population that is recovered (i.e., no longer contagious)
a
the constant infection rate
the constant rate of recovery
dS
(a) Solve the differential equation
-aS.
(b) Substitute your answer from (a) into the differential equation 4 = aS – bI and then solve for I.
dI
dt
(c) Substitute your answer from (b) into the differential equation
dR
dt
bI and then solve for R.
(d) Identify the general solution to the simplified SIR model in (2).
(e) Suppose there is an outbreak of malaria in Central America. If the typical rate of recovery for
malaria is b = 2 and preliminary studies estimate the infection rate is between 0.03 < a < 0.07,
plot the graphs of S(t), I(t), R(t) on the same axes. State the value of a that you
used.
(f) Compare the graphs of S(t), I(t), R(t) for several values of a. Describe in words how does the
a-value affect your solutions?
Transcribed Image Text:Here we will consider the following simplified version of the model: dS – -aS dt dI dt aS – bI (2) dR dt where the functions S(t), I(t), R(t) and the constants a, b > 0 represent: S(t) the percentage of the population that is susceptible (i.e., has not contracted the disease) I(t) the percentage of the population that is infected (i.e., contagious) R(t) the percentage of the population that is recovered (i.e., no longer contagious) a the constant infection rate the constant rate of recovery dS (a) Solve the differential equation -aS. (b) Substitute your answer from (a) into the differential equation 4 = aS – bI and then solve for I. dI dt (c) Substitute your answer from (b) into the differential equation dR dt bI and then solve for R. (d) Identify the general solution to the simplified SIR model in (2). (e) Suppose there is an outbreak of malaria in Central America. If the typical rate of recovery for malaria is b = 2 and preliminary studies estimate the infection rate is between 0.03 < a < 0.07, plot the graphs of S(t), I(t), R(t) on the same axes. State the value of a that you used. (f) Compare the graphs of S(t), I(t), R(t) for several values of a. Describe in words how does the a-value affect your solutions?
4. During the recent pandemic, there has been a lot of discussion about the SIR model (Susceptible-
Infected-Recovered) to describe the spread of disease.
dS
dt
= -aSI
dI
dt
aSI – BI
(1)
dt
BI
where a, B > 0 describe the transmission rate and the recovery rate, respectively. Although an explicit
solution to the SIR model is known, it is an analytical solution (an integral solution that can only be
evaluated numerically). If you want to learn more about epidemiology and the SIR model, see Trefor
Bazett's video:
The Math of Epidemics / Intro to the SIR Model
Transcribed Image Text:4. During the recent pandemic, there has been a lot of discussion about the SIR model (Susceptible- Infected-Recovered) to describe the spread of disease. dS dt = -aSI dI dt aSI – BI (1) dt BI where a, B > 0 describe the transmission rate and the recovery rate, respectively. Although an explicit solution to the SIR model is known, it is an analytical solution (an integral solution that can only be evaluated numerically). If you want to learn more about epidemiology and the SIR model, see Trefor Bazett's video: The Math of Epidemics / Intro to the SIR Model
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