Question

What type of exponential growth is this problem?
http://pasteboard.co/yXACRcjM.png

Answer 1

It took 5 years to grow by a factor of 4800/4000, so the exponential function can be written as
\[P(t) = 4000(4800/4000)^{t/5}\]

You may plugin t = 15 to get the bacteria count after 15 hours