Question

there are 2,100 bacteria in a circular petri dish. the dish has a radius of 40 millimeters. what is the approximate population density? (use 3.14 for $pi$)
area of a circle = $pi r^{2}$
0.02 bacteria per square millimeter
0.42 bacteria per square millimeter
52.5 bacteria per square millimeter

Explanation:

Answer:

1. Discipline and Sub - field: Natural Science (Biology, as it involves bacteria population density calculation which is a common concept in biological studies related to microbiology)
2. Answer: First, calculate the area of the circular petri - dish using the formula \(A=\pi r^{2}\). Given \(r = 40\) mm and \(\pi=3.14\), then \(A = 3.14\times40^{2}=3.14\times1600 = 5024\) square millimeters.

The population density \(D=\frac{N}{A}\), where \(N = 2100\) bacteria. So \(D=\frac{2100}{5024}\approx0.42\) bacteria per square millimeter. So the answer is 0.42 bacteria per square millimeter.