there are 2,100 bacteria in a circular petri dish. the dish has a radius of 40 millimeters. what is the…

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 $pi$)\narea of a circle = $pi r^{2}$\no 0.02 bacteria per square millimeter\no 0.42 bacteria per square millimeter\no 2.39 bacteria per square millimeter\no 52.5 bacteria per square millimeter

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 $pi$)\narea of a circle = $pi r^{2}$\no 0.02 bacteria per square millimeter\no 0.42 bacteria per square millimeter\no 2.39 bacteria per square millimeter\no 52.5 bacteria per square millimeter

Answer

Explanation:

Step1: Calculate the area of the petri - dish

The formula for the area of a circle is $A = \pi r^{2}$. Given $r = 40$ mm and $\pi=3.14$, we have $A=3.14\times40^{2}=3.14\times1600 = 5024$ square millimeters.

Step2: Calculate the population density

Population density $d=\frac{\text{Number of bacteria}}{\text{Area}}$. There are 2100 bacteria and the area $A = 5024$ square millimeters. So $d=\frac{2100}{5024}\approx0.42$ bacteria per square millimeter.

Answer:

B. 0.42 bacteria per square millimeter