 # Find Circumferences of Circles Using Their Radii (1)

In this worksheet, students use formulae to calculate the circumferences of circles given their radii. Key stage:  KS 3

Curriculum topic:  Geometry and Measures

Curriculum subtopic:  Solve Problems Involving Perimeters and Areas of 2D Shapes

Difficulty level:   ### QUESTION 1 of 10

This worksheet is about finding the circumferences of circles.

The circumference of a circle is its perimeter or the distance around its edge.

You must learn these two important formulae for a circle of radius, r or diameter, d:

Circumference of a circle = 2πr

Circumference of a circle = πd  Example 1

Find the circumference of a circle of radius 6 cm.

Circumference = 2 × π × r = 2 × π × 6 = 12 × π = 37.7 cm  (1 dp)

Example 2

Find the circumference of a circle of diameter 6 cm.

Circumference = π × d = π × 6 = 18.8 cm  (1 dp)

Find the circumference of a circle of radius 25 cm.

(Just write the number to 1 decimal place)

Find the circumference of a circle of radius 5 cm.

(Just write the number to 1 decimal place)

Find the circumference of a circle of radius 7 cm.

(Just write the number to 1 decimal place)

Find the circumference of a circle of radius 10 cm.

(Just write the number to 1 decimal place)

Find the circumference of a circle of radius 3.5 cm.

(Just write the number to 1 decimal place)

Find the circumference of a circle of diameter 4 cm.

(Just write the number to 1 decimal place)

Find the circumference of a circle of diameter 10 cm.

(Just write the number to 1 decimal place)

Find the circumference of a circle of diameter 14 cm.

(Just write the number to 1 decimal place)

Find the circumference of a circle of diameter 12 cm.

(Just write the number to 1 decimal place)

Find the circumference of a circle of diameter 42 cm.

(Just write the number to 1 decimal place)

• Question 1

Find the circumference of a circle of radius 25 cm.

(Just write the number to 1 decimal place)

157.1
EDDIE SAYS
2 × π × 25
• Question 2

Find the circumference of a circle of radius 5 cm.

(Just write the number to 1 decimal place)

31.4
EDDIE SAYS
2 × π × 5
• Question 3

Find the circumference of a circle of radius 7 cm.

(Just write the number to 1 decimal place)

44.0
EDDIE SAYS
2 × π × 7
• Question 4

Find the circumference of a circle of radius 10 cm.

(Just write the number to 1 decimal place)

62.8
EDDIE SAYS
2 × π × 10
• Question 5

Find the circumference of a circle of radius 3.5 cm.

(Just write the number to 1 decimal place)

22.0
EDDIE SAYS
2 × π × 3.5
• Question 6

Find the circumference of a circle of diameter 4 cm.

(Just write the number to 1 decimal place)

12.6
EDDIE SAYS
π × 4
• Question 7

Find the circumference of a circle of diameter 10 cm.

(Just write the number to 1 decimal place)

31.4
EDDIE SAYS
π × 10
• Question 8

Find the circumference of a circle of diameter 14 cm.

(Just write the number to 1 decimal place)

44.0
EDDIE SAYS
π × 14
• Question 9

Find the circumference of a circle of diameter 12 cm.

(Just write the number to 1 decimal place)

37.7
EDDIE SAYS
π × 12
• Question 10

Find the circumference of a circle of diameter 42 cm.

(Just write the number to 1 decimal place)

131.9
EDDIE SAYS
π × 42
---- OR ----

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