# Circumference Problems

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Circumference problems are the problems in which we need to calculate the circumference of a circle. It is

calculated by the formula: - 2 x pie x r. Here 2 and pie (= 22/7 or 3.14) are constants, hence they don’t have

any units. And r is the radius of circle which is generally measured in metre (m) or centimetre (cm). Since the

unit of circumference depends upon the radius so the unit of circumference is m or cm

This can be understood by the detailed examples, which are shown below:-

Example 1:- Find the Circumference of circle when diameter is 7000 cm.

Solution:- Given the diameter of circle, d is 7000 cm.

So the radius of circle is (radius is always half of the diameter), r = 7000/2 = 7000/2  3500 cm.

Now circumference of circle = 2 x pie x r

Therefore Circumference of circle, C = 2 x 22/7 x 3500

So C = 22000 cm.

Hence the circumference of circle = 22000 cm.

Example 2:- Find the Circumference of circle when diameter is 42 cm.

Solution:- Given the diameter of circle, d is 42 cm.

So the radius of circle is, r = d/2 = 42/2 = 21 cm.

Now circumference of circle = 2 x pie x r

Therefore Circumference of circle, C = 2 x 22/7 x 21

So C = 132 cm.

Hence the circumference of circle = 132 cm.