There are 2 comma 100 bacteria in a circular petri dish. The dish has a radius of 40 millimeters. What is the approximate population density? (Use 3 point 1 4 for pi ) Area of a circle is equal to pi r squared

First find the dish’s area: 3.14 × 40² = 3.14 × 1,600 = 5,024 square millimeters. Divide the 2,100 bacteria by the area: 2,100 ÷ 5,024 ≈ 0.42 bacteria per square millimeter. Therefore, the approximate population density is 0.42 bacteria per square millimeter, choice D.

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