CPM Homework Help : CALC Problem 11-13

Multiple Choice: As a rumor spreads across a city, its rate is proportional to the product of the number of citizens who have heard the rumor and the number who have not. Which equation below could represent this scenario?

Hint:

The rumor is spreading throughout the population over time. What variables should be used?
If $P$ represents the number of people that have heard the rumor, what is a possible expression for the number of people that have not heard the rumor?

$\frac { d P } { d t } = k P ( 350,000 - P )$

$\frac { d P } { d x } = k x ( 350,000 - x )$

$\frac { d P } { d t } = k t ( 350,000 - t )$

$\frac { d P } { P } = k ( 350,000 - t ) d t$

None of these