Question

A colony of germs grows exponentially. It starts at 500 germs. After 8 minutes there are 600 germs. When will there be 1000 germs?

Answer 1

600=500e^a8 where a is a constant.
1000=600e^aX

solve for a in the first equation:
1.2=e^8a
take ln of both sides
8a=.182
a=.02279

now put that in the second equation

1000/600=e^ax
take ln both sides
.511=ax= .02279x
x=22.4 min from when it was 600,or 30.4 min from the start.

check my work