A  bacterium can divide every 20 minutes.  Beginning with a  single individual,  how many bacteria will be there in the population if there is exponential growth for 3 hours?
Given information: A bacterium can divide every 20 minutes (3/hour)

Thus, in 3 hours, it will totally divide 3/hour x 3 hours = 9 times
Thus, 9 times multiplication will successively yield 2, 4, 8, 16, 32, 64, 128, 256, 512 bacteria.
So at the end of 9 hours, there will be 512 bacteria.
18
440
512
1024