SOLUTION: Please help. Show step by step. Thanks A bacteria culture starts with 500 bacteria and grows at a rate proportional to its size. After 3 hours there will be 1500 bacteria.

Algebra ->  Exponential-and-logarithmic-functions -> SOLUTION: Please help. Show step by step. Thanks A bacteria culture starts with 500 bacteria and grows at a rate proportional to its size. After 3 hours there will be 1500 bacteria.       Log On


   



Question 998640: Please help. Show step by step. Thanks
A bacteria culture starts with 500 bacteria and grows at a rate proportional to its size. After 3 hours there will be 1500 bacteria.
(a) Express the population P after t hours as a function of t .
P(t) =
(b) What will be the population after 5 hours?
bacteria
(c) How long will it take for the population to reach 2130? Give your answer accurate to at least 2 decimal places.

Answer by KMST(5328) About Me  (Show Source):
You can put this solution on YOUR website!
That is what we cal exponential growth.
We like to express it as
P%28t%29=P%5B0%5D%2Ae%5Ekt based on
P%5B0%5D= the initial population,
k= a rate constant that we will find, and
e= and irrational number.
We could use any other base, as in
P%28t%29=P%5B0%5D%2A10%5EKt , with a power of base 10 ,
and a different constant K .
However, we really like to use the number e as a base,
because it makes the growth rate
dP%2Fdt=k%2AP%28t%29 ,
making k the ratio of the growth rate to the population size.

(a) So, with P%5B0%5D=500 and P%283%29=1500 ,
500%2Ae%5E%283k%29=1500-->e%5E%283k%29=1500%2F500-->e%5E%283k%29=3-->3k=ln%283%29-->k=ln%283%29%2F3 , and
highlight%28P%28t%29=500%2Ae%5E%28%22ln%283%29t%2F3%22%29%29<-->highlight%28P%28t%29=500%2A3%5E%28%22t%2F3%22%29%29<-->highlight%28P%28t%29=500%2Aroot%283%2C3%5Et%29%29
(b) P%285%29=500%2Ae%5E%28%225ln%283%29%2F3%22%29=highlight%283120%29(rounded)
(c) 500%2Ae%5E%28%22ln%283%29t%2F3%22%29=2130-->e%5E%28%22ln%283%29t%2F3%22%29=2130%2F500-->e%5E%28%22ln%283%29t%2F3%22%29=4.26-->ln%283%29t%2F3=ln%284.26%29-->t%2F3=ln%284.26%29%2Fln%283%29-->t=3ln%284.26%29%2Fln%283%29-->highlight%28t=3.96%29(rounded)