One model for the spread of a rumor is that the rate of spread is proportional to the product of the fraction y of the population who have heard the rumor and the fraction who have not heard the rumor. (a) Write a differential equation that is satisfied by y. (Use k for the constant of proportionality.) dy dt =     (b) Solve the differential equation. (Let y(0) = y0.)

Advanced Engineering Mathematics
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Chapter2: Second-order Linear Odes
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One model for the spread of a rumor is that the rate of spread is proportional to the product of the fraction y of the population who have heard the rumor and the fraction who have not heard the rumor.

(a) Write a differential equation that is satisfied by y. (Use k for the constant of proportionality.)
dy
dt
 =
 
 


(b) Solve the differential equation. (Let
y(0) = y0.)

 
 


(c) A small town has 3500 inhabitants. At 8 AM, 280 people have heard a rumor. By noon half the town has heard it. At what time will 90% of the population have heard the rumor? (Do not round k in your calculation. Round your final answer to one decimal place.)
hours after 8 AM
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