Perimeter is the distance around a closed figure. It can be measured in millimetres (mm), centimetres (cm), metres (m) and kilometres (km).

The relation between these are related as follows:

10 mm = 1 cm

100 cm = 1 m

1000 m = 1 km

The word 'perimeter' is sometime used in the place of “circumference” also.

**When the radius of a circle is given, **the circumference or perimeter can be calculated using the formula bwloe:

Perimeter (P) = 2 · π · R

where:

R is the radius of the circle

π is Pi, approximately 3.142

**When the diameter of a circle** is given, the circumference can be found using the formula

Perimeter (P) = π · D

where:

D is the diameter of the circle

π is Pi, approximately 3.142

**When the area of a circle is given**, the circumference can be found using the formula:

Perimeter (P) = √(4 · π · A )

where:

A is the area of the circle

π is Pi, approximately 3.142

A circular shape has a radius of 10 m. Find the perimeter/circumference of the shape.

**Solution:**

P = 2 · π · R

P = 2 · 3.1416 · 10

P = 62.832 m

So, the perimeter/circumference of the shape is = 62.832 m.

**Example 2:** Find the perimeter of the given circle whose diameter is 12.4 cm.

**Solution:**

Diameter of the circle (D) = 12.4 cm.

Formula to find the perimeter of the circle when the diameter is given

Π* D.

Substitute the diameter 12.4 and Pi value as 3.14 in the above formula.

Perimeter = (3.14)(12.4) = 38.936

Therefore 38.936 cm is the perimeter of the given circle.