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 π)


0.02 bacteria per square millimeter
0.42 bacteria per square millimeter
2.39 bacteria per square millimeter
52.5 bacteria per square millimeter

Answer 1

Dear Markus,

◆ Answer -

(b) Population density ≈ 0.42 bacteria/sq.mm

● Explaination -

# Given -

N = 2100 bacteria

r = 40 mm

# Solution -

Area of the petri dish is calculated as -

A = πr^2

A = 3.14 × 40^2

A = 5024 mm^2

Population density of the bacterial colonies is calculated as -

Population density = Number of bacteria / area

Population density = N / A

Population density = 2100 / 5024

Population density = 0.418 bacteria/sq.mm

Population density ≈ 0.42 bacteria/sq.mm

Therefore, population density of bacterial colonies in petri dish will be 0.42 bacteria/sq.mm .

Best luck...