Answer: Hello there!
We know that the culture has 2000 bacteria initially (at t = 0 min), and it doubles when t = 40min, again at t = 80 min, and so on
And the rate of grouth is proportional to the population, then we can obtain an expression of the form:
P(t) = 2000*k(t) where k(t) is the factor that defines the growth of the population:
we know that:
p(0) = 2000*k(0) = 2000
p(40) = 2000*k(40) = 2000*2 = 4000
p(80) = 2000*k(80) = 2000*2*2 = 8000
etc
then we can see that k(t) = 2^(t/40)
where k(0) = 1, k(40) = 2, k(80) = 2*2, etc
then the function that models the population of the culture is:
p(t) = 2000*2^(t/40)
where t is in minutes.
