Question

The population of a community is known to increase at a rate proportional to the number of people present at time t. The initial population P0 has doubled in 5 years. Suppose it is known that the population is 12,000 after 3 years. What was the initial population P0?

Answer 1

Answer:

P(0) = 7,917

Step-by-step explanation:

The population of the community is given by the following formula:

$P(t) = P(0)(1+r)^{t}$

In which P(0) is the initial population and r is the growth rate.

The initial population P0 has doubled in 5 years.

This means that

$P(5) = 2P(0)$

Which lets us find r.

$P(t) = P(0)(1+r)^{t}$

$2P(0) = P(0)(1+r)^{5}$

$(1+r)^{5} = 2$

Applying the 5th root to both sides

$1+r = 1.1487$

$r = 0.1487$

So

$P(t) = P(0)(1.1487)^{t}$

Suppose it is known that the population is 12,000 after 3 years.

With this, we find P(0)

$P(t) = P(0)(1.1487)^{t}$

$12000 = P(0)(1.1487)^{3}$

$1.5157P(0) = 12000$

$P(0) = \frac{12000}{1.5157}$

$P(0) = 7917$