Question

The rate of change (dP/dt), of the number of people on an ocean beach is modeled by a logistic differential equation. The maximum number of people allowed on the beach is 1200. At 10 A.M., the number of people on the beach is 200 and is increasing at the rate of 400 per hour. Whats the differential equation which can describe this situation?

Answer 1

Answer:

$\frac{dP}{dt} = 2.4P(1 - \frac{P}{1200})$

Step-by-step explanation:

The logistic differential equation is as follows:

$\frac{dP}{dt} = rP(1 - \frac{P}{K})$

In this problem, we have that:

$K = 1200$, which is the carring capacity of the population, that is, the maximum number of people allowed on the beach.

At 10 A.M., the number of people on the beach is 200 and is increasing at the rate of 400 per hour.

This means that $\frac{dP}{dt} = 400$ when $P = 200$. With this, we can find r, that is, the growth rate,

So

$\frac{dP}{dt} = rP(1 - \frac{P}{K})$

$400 = 200r(1 - \frac{200}{1200})$

$166.67r = 400$

$r = 2.4$

So the differential equation is:

$\frac{dP}{dt} = rP(1 - \frac{P}{K})$

$\frac{dP}{dt} = 2.4P(1 - \frac{P}{1200})$