Circumference of a circle is the distance around the circle.

Formula :

**Circumference of Circle = 2**π**r**

Here the value of π is either 22/7 or 3.14 and "r" stands for radius of a circle.

**Example 1:**

Find the circumference of a circle whose radius is 14 cm.

**Solution:**

Formula for circumference of circle is

= 2πr

Substitute π = 22/7 and r = 14.

≈ 2 x (22/7) x 14

= 2 x 22 x 2

= 88

So, circumference of the given circle is about 88 cm.

**Example 2:**

Find the diameter of circle with circumference is 88 cm.

**Solution:**

Circumference of circle = 88 cm

2πr = 42

2 x (22/7) x r = 42

(44/7) x r = 42

Multiply each side by 7/44.

r = 88 x (7/44)

r = 2 x 7

r = 14

Then, diameter is

= 2 x radius

= 2 x 14

= 28 cm

**Example 3 :**

Find the circumference of a circle with an area of 441π square feet.

**Solution :**

Area of the circle = 441π ft^{2}

πr^{2 }= 441π

Divide each side by π.

r^{2} = 441

r = 21

Formula for circumference of circle is

= 2πr

Substitute π = 22/7 and r = 21.

≈ 2 x (22/7) x 21

= 2 x 22 x 3

= 132

So, circumference of the given circle is about 132 ft.

**Example 4 :**

The moon is about 384000 km away from the earth and its path around the earth is nearly circular. Find the distance traveled by the moon every month.

**Solution :**

Because the path of the moon around the earth is nearly circle, the distance traveled by the moon every month is the circumference of the circle.

**Given :** The moon is about 384000 km away from the earth

Then radius is 384,000.

Formula for circumference of circle is

= 2πr

Substitute π = 22/7 and r = 38400.

≈ 2 x 3.14 x** **384,000

= 2,411,520

So, the distance traveled by the moon every month is about 2,411,520 km.

**Example 5 :**

A copper wire is in the form of a circle with radius 35 cm. If it is bent into a square, find the length of each side of the square.

**Solution :**

**Given :** Radius of a circle is 35 cm.

Since the same wire is bent into the form of a square,

Circumference of the circle = Perimeter of the square

Circumference of circle is

= 2πr

Substitute π = 22/7 and r = 35.

≈ 2 x (22/7) x** **35

= 2 x 22 x 5

= 220

Then,

perimeter of the square = 220 cm

4a = 220

Divide each side by 4.

a = 55

So, the length of each side of the square is 55 cm.

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