a culture started with 2,000 bacteria. After 4 hours, it grew to 2,200 bacteria. Predict how many bacteria will be present in 9 hours. round

Assuming a regular rate:

Final Amount  =  (Initial Amount) x (rate ^ time)

           2200  =  2000 · r^4

Dividing by 2000:         1.1  =  r^4

Finding the fourth root:    r  =  1.024

After 9 hours:  Final Amount  =  2000 · 1.024^9

     --->   Final Amount  =  2478