ANSWER
Approximately after 15 minutes.
EXPLANATION
The growth rate of the first bacteria is

The growth rate of the first bacteria :

To find the time that, there will be an equal number of bacteria, we equate the two equation;



We solve for t to get,

Or

We discard the negative value.
This implies that,

The volume of a cylinder is given by the product of its base area (i.e. the area of a circle) and its height:

Solving for r, we have

Plugging the numbers, we have
