The diameter of a bacterial colony that doubles every hour is represented by the graph below. what is the diameter of the bacteria after 9 hours?
(0,1) , (1,2) , (2,4) , (3,8)

The colony doubles every hour, the population is equal to
p = 2^t

Where t is the time in hours.
We are able to see this because:
2^0 = 1
2^1 = 2
2^2 = 4

Notice that the x coordinate of the graph corresponds to the time, and the y coordinate corresponds to the population.

Thus at t = 9
p = 2^t
p = 2^9
p = 512.

The correct answer is 512.

Technically speaking, histograms are another version of bar charts, if you need to work one out then skim through google hope-o that -o!