Question

In 2006, there were approximately 233 million cell phone subscribers in the United States. During the next 4 years, the number of cell phone subscribers increased by about 6% each year.
a. Write an exponential growth model giving the number of cell phone subscribers y (in millions) t years after 2006.

Answer 1

The general formula for an exponential growth is:
F = P( 1 + i ) ^t
where F is the future amount in t years
P is the present amount
i is the fraction of increase per time
t is the time

for the increase cellphone subscriber
P = 233
i = 0.06
so
F = 233 ( 1 + 0.06)^t
F = 233 ( 1.06)^t