Answer:
Step 1:
Let's set up the equation.
Initial value = 500,000
Decay rate per hour = 0.05
Hours = 48
So our equation is:

Step 2:
We then input this into a calculator and get 42628.7951671541.
Final Answer:
42628.7951671541 or 42,629 bacteria, depending on whether you need the decimal or need to round it.