Question

Rumor of the cancellation of final exams began to spread one day on a college campus with a population of 80 thousand students.Suppose that one thousand students initially heard the rumor via a text message. Within a day, 10 thousand students had heard therumor. Assume that the increase in the number of peopleP(in thousands) who had heard the rumor is directly proportional to thenumber of people who have heard the rumor and the number of people who have not heard the rumor. DetermineP(t).

Answer 1

P(t) is directly proportional to N and N'.

Where P is the increase in numbers of students who have heard the exam's cancellation rumor at any time t;

N is numbers of students who have heard the rumor of the exam's cancellation;

N' is numbers of students who have not heard the rumor of the exam's cancellation;

N' = (80 - N). Since the total number of students is 80;

K is the constant of the proportionality.

K is calculated to be 9/700

Therefore,

P(t) = KNN'

P(t) = (9/700) x N x (80 - N)

Explanation:

The total number of students is 80. For N, N' = 80 - N.

Initially, 1 thousand people heard the rumor.

Within/after a day, the increased in number of students who have heard the rumor is P = 10 - 1 = 9

P = 9 = K x 10x (80-10)

9 = K x 10 x 70 = 700K.

Divide both sides by 700,

9/700 = (700/700)K

K = 9/700

Subtitle K into the equation P(t) = KNN'

P(t) = (9/700) x N x N'

P(t) = (9/700) x N x (80 - N), where N' = 80 - N