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A rumor spreads through a small town. Let y(t) be the fraction of the population that has heard the rumor at time t and assume t

sladkih [1.3K]

Answer:

The answer is shown below

Step-by-step explanation:

Let y(t) be the fraction of the population that has heard the rumor at time t and assume that the rate at which the rumor spreads is proportional to the product of the fraction y of the population that has heard the rumor and the fraction 1−y that has not yet heard the rumor.

a)

$\frac{dy}{dt}\ \alpha\ y(1-y)$

$\frac{dy}{dt}=ky(1-y)$

where k is the constant of proportionality, dy/dt = rate at which the rumor spreads

b)

$\frac{dy}{dt}=ky(1-y)\\\frac{dy}{y(1-y)}=kdt\\\int\limits {\frac{dy}{y(1-y)}} \, =\int\limit {kdt}\\\int\limits {\frac{dy}{y}} +\int\limits {\frac{dy}{1-y}} =\int\limit {kdt}\\\\ln(y)-ln(1-y)=kt+c\\ln(\frac{y}{1-y}) =kt+c\\taking \ exponential \ of\ both \ sides\\\frac{y}{1-y} =e^{kt+c}\\\frac{y}{1-y} =e^{kt}e^c\\let\ A=e^c\\\frac{y}{1-y} =Ae^{kt}\\y=(1-y)Ae^{kt}\\y=\frac{Ae^{kt}}{1+Ae^{kt}} \\at \ t=0,y=10\%\\0.1=\frac{Ae^{k*0}}{1+Ae^{k*0}} \\0.1=\frac{A}{1+A} \\A=\frac{1}{9} \\$

$y=\frac{\frac{1}{9} e^{kt}}{1+\frac{1}{9} e^{kt}}\\y=\frac{1}{1+9e^{-kt}}$

At t = 2, y = 40% = 0.4

c) At y = 75% = 0.75

$y=\frac{1}{1+9e^{-0.8959t}}\\0.75=\frac{1}{1+9e^{-0.8959t}}\\t=3.68\ days$

5 0

3 years ago

Abdul uses 15 1/2 cups of flour to make 3 loaves of bread. At that rate, how many cups of flour would Abdul need to make 4 loave

Pavlova-9 [17]

Yea don’t click on the links the get information from u

3 0

3 years ago

A number is multiplied by 2, and then 5 is subtracted. The result is 43.

irga5000 [103]

Answer: The answer is 7.

5 0

3 years ago

Hannah can paint a room in 20 hours. Destiny can paint the same room in 12 hours. How long does it take for both Hannah and Dest

KonstantinChe [14]

Hello!

I believe the answer is they can, together, paint the room in 8.9hrs.

Hope this helps! ☺♥

6 0

3 years ago

What is the answer of this equation ? 10x-6(2x+5)=20

Rudiy27

Answer:

Simplifying

x = -25

Step-by-step explanation:

Reorder the terms:

10x + -6(5 + 2x) = 20

10x + (5 * -6 + 2x * -6) = 20

10x + (-30 + -12x) = 20

Reorder the terms:

-30 + 10x + -12x = 20

Combine like terms: 10x + -12x = -2x

-30 + -2x = 20

Solving

-30 + -2x = 20

Solving for variable 'x'.

Move all terms containing x to the left, all other terms to the right.

Add '30' to each side of the equation.

-30 + 30 + -2x = 20 + 30

Combine like terms: -30 + 30 = 0

0 + -2x = 20 + 30

-2x = 20 + 30

Combine like terms: 20 + 30 = 50

-2x = 50

Divide each side by '-2'.

x = -25

6 0

3 years ago