Answer:
About 24 hours.
Explanation:
We are given that the experiment initially had 100 bacteria cells, and that its populations double every 15 hours.
From the given formula:

We can substitute 100 for Pâ‚€ and 15 for t. This yields:

We want to find after how many hours t will the population reach 300.
So, let's substitute 300 for P_t and solve for t:

Divide:

We can take the natural log of both sides:

Logarithm properties:

Solve for t:

Use a calculator:

In conclusion, the population will reach 300 bacteria after about 24 hours.