The formula for finding the circumference is the diameter times pi
because the radius is half of the diameter, the diameter of this circle would be 8
8 times pi equals approximately 25.1327
Or you could leave it in terms of pi and say 8pi (using the symbol)
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circumference = 2*pi*4 inches
Multiply the radius by 2 to get the diameter. Then multiply the diameter by pi to get the circumference. Example: If radius = 2 inches, diameter = 4 inches circumference = 4 x pi = 4 (3.1416) or about 12.57 inches
Circumference is pi * r * 2. Area is pi * r2. In your circle, both r * 2 and r2 equal 4. Your radius is 2 inches.
If the circumference of the circle is 4 inches then the radius = 4/(2*pi) = 0.6366197724 inches And the area of the circle = pi*0.63661977242 = 1.273239545 or about 1.273 square inches
The circumference of a circle can be found with this formula: Circumference = 2*(radius)*∏ where ∏ can be rounded to 3.14 Plugging in your radius of 4: Circumference = 2*4*∏ = 8*∏ which is around 25.13.