# How long does it take the culture to double its mass if a bacterial culture which is growing exponentially increases from 5 g to 7 g in 11 hours?

##### 1 Answer

Feb 22, 2015

This is an example of a *exponential function.*

The form is always

Where

Now we fill in what we know:

Now grow factor

You can do this on your calculator by

The growth factor can then be used in the equation:

From here on there are two ways to go:

(1) put this equation in your GC as Y1= and intersect with Y2=2

(2) Use logarithms:

**Answer** : a bit more than 22 hours. This is the doubling time from *any* start situation.