# Thread: exponential growth and decay help plz

1. ## exponential growth and decay help plz

I am stuck on this problem..i would really appreciate any help.
If the world population is 1990 was 4.5billion and it is growing exponentially with a growth constant k = (ln3)/8, estimate the world population in the year 2014.
im thinking to use y = Ce^(kx)
but I have trouble with these types of problems.
Thanks for the help!

2. Originally Posted by davecs77
I am stuck on this problem..i would really appreciate any help.
If the world population is 1990 was 4.5billion and it is growing exponentially with a growth constant k = (ln3)/8, estimate the world population in the year 2014.
im thinking to use y = Ce^(kx)
but I have trouble with these types of problems.
Thanks for the help!
use $y = Ce^{kt}$

where y is the population at time t, k is the growth constant, C is the initial population, and t is the time. thus we have:

$y = 4.5e^{\ln (3) t/8}$ for y in billions.

now plug in t = 24 (since we start at 1990 and go to 2014)and solve for y