First you need to find the area of the plate.
The formula for the area of a circle is Area = pi *r^2
The radius (r) is given as 6 inches.
We will use 3.14 for pi
Area = 3.14 x 6^2
Area = 3.14 x 36
Area = 113.04 square inches.
Now to find the density, divide the total bacteria by the area:
Density = 120,000 / 113.04 = 1061.57 which rounds up to 1,062 bacteria/ square inch.
