the circumference of an 18mm circle

Question

I'm struggling in the "Circle-Circumference And Area" unit an i've tried to answer it but i dont know if im doing it riht and i have a quiz tomorrow..please help me!

Answer 1

If you mean "find the circumference of a circle with a diameter of 18 mm" then:

Circumference = Pi * Diameter

C = 18 * 3.14 (approximate value for Pi)

C = 56.52 mm

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If you mean "find the circumference of a circle with an area of 18 mm^2" then:

Area = Pi * Radius^2

Area / Pi = Radius^2

18/3.14 = Radius^2

5.73 = Radius^2

2.39 = Radius

Circumference = 2 * Pi * Radius

Circumference = 2 * 3.14 * 2.39

Circumference = 15.01

The circumference should be about 15 mm.