posted by Garz .
A certain bacterium divides into 2 bacteria every 20 minutes. If there are four bacteria in the culture now, how many will there be in 4 hours, assuming that no bacteria die?
population doubles every 20 minutes, or 3 times per hour. So, every hour, the population grows by a factor of 8.
So, since we are starting at p(0) = 4,
p(h) = 4*8^h
gives the population after h hours.
p(4) = 4*8^4 = 4*4096 = 16384