find the circumference of a circle whose radius is:

1. 8 inches

2. 4 inches

http://www.khanacademy.org/math/geometry/basic-geometry/circum_area_circles/v/circles--radius--diameter-and-circumference

Watch this teaching video. Take notes; replay if needed; work it out.

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To find the circumference of a circle, you can use the formula:

Circumference = 2 * π * radius

where π (pi) is a mathematical constant approximately equal to 3.14159.

Let's calculate the circumference for the given radii:

1. Radius = 8 inches
Circumference = 2 * π * 8 inches
Note: Since the value of π is an irrational number, we will use an approximate value of 3.14159 for calculation.
Circumference = 2 * 3.14159 * 8 inches
Circumference ≈ 50.26544 inches

Therefore, the circumference of a circle with a radius of 8 inches is approximately 50.26544 inches.

2. Radius = 4 inches
Circumference = 2 * π * 4 inches
Circumference = 2 * 3.14159 * 4 inches
Circumference ≈ 25.13272 inches

Therefore, the circumference of a circle with a radius of 4 inches is approximately 25.13272 inches.