Instead of doing your problem for you, I'll do a different one that is done
exactly the same way, step by step.
I'll do this one:
The population of germs on a toilet seat triples every 20 mins. How long to the nearest minute, would it take for the population to quadruple?
P0 = original population
P = the population after t minutes.
The population of germs on a toilet seat triples every 20 mins.
When P=20, P=3∙P0
Substitute in
Divide both side by P0
Take natural logs of both sides:
Substitute in
How long to the nearest minute, would it take for the population to quadruple?
Substitute
P=4∙P0
Divide both side by P0
Take natural logs of both sides:
To the nearest minute, every 25 minutes.
Now do yours exactly the same way, step by step.
Edwin