Math CentralQuandaries & Queries


Question from Marcy:

The diameter of the circle is 12cm. I need to convert the diameter to m2.

Hi Marcy,

Since you are asking for square metres I expect that you want the area of the circle. The area of a circle is given by

area = π r2

where r is the radius and π is approximately 3.1416. The radius is half the diameter so you have a radius of 12/2 = 6 cm. You want square metres not square centimeters so you need to convert the radius to metres. There are 100 centimeters in a metre so 6 cm = 6/100 = 0.06 m. Thus the area of your circle is

π r2 = 3.1416 × 0.062 = 0.0113 m2


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