 # Understand Circle Parts

In this worksheet, students will be asked to find parts of a circle, the diameter, radius and circumference. Key stage:  KS 2

Curriculum topic:   Geometry: Properties of Shapes

Curriculum subtopic:   Know Circle Parts

Difficulty level:   ### QUESTION 1 of 10

This activity is going to ask you to complete different questions all about circles.

A circle is a 2D shape, every point on a circle has the same fixed distance to the centre.

In Year 6, we learn about the parts of a circle.

Let's recap:

Diameter

This circle shows the diameter, this is the length of the line through the centre, from one edge to another. This circle shows the radius, the radius is the distance from the centre of the circle to the outer edge.

The radius is half of the diameter so is fairly straightforward to calculate. Circumference

A circle's circumference is the distance around the edge. How to find the circumference of a circle

To find the circumference of a circle we have to use the formulae:

(2 x x r) = pi = 3.14

Example: So, let's find the circumference of this circle.

(2 x 3.14 x 5) =

(6.28 x 5) = 31.4

The circumference is 31.4cm

Look at this circle.

What does the letter 'C' show? Look at this circle.

Type what letter 'C' shows Look at the circle.

What does letter b show? Look at the circle.

The diameter of this circle is 64m. Look at the circle.

What is the length of the diameter? Look at this circle.

What is the circumference?

The formulae is (2 x x r)

Remember = 3.14 81.46 cm

81.64 cm

81.14 cm

81.16 cm

Look at this circle.

What is the circumference?

The formulae is (2 x x r)

Remember = 3.14 94.02 cm

94.12 cm

95.2 cm

94.2 cm

Look at this circle.

What is the circumference?

The formulae is (2 x x r)

Remember = 3.14 94.02 cm

94.12 cm

95.2 cm

94.2 cm

Look at this circle.

The diameter is 6m.

What is the circumference?

The formulae is (2 x x r)

Remember = 3.14 94.02 cm

94.12 cm

95.2 cm

94.2 cm

Look at this circle.

What is the circumference?

The formulae is (2 x x r)

Remember = 3.14 • Question 1

Look at this circle.

What does the letter 'C' show? Circumference
The circumference
EDDIE SAYS
The letter C shows the circumference, the measurement all the way around the circle.
• Question 2

Look at this circle.

Type what letter 'C' shows Diameter
The diameter
EDDIE SAYS
This time, letter c shows the diameter. The diameter is the straight line going through the centre of the circle, connecting two points on the circumference.
• Question 3

Look at the circle.

What does letter b show? EDDIE SAYS
Letter b shows the radius of the circle. The radius is the distance from the centre of the circle to the edge of the circle The radius is half of the diameter in length.
• Question 4

Look at the circle.

The diameter of this circle is 64m. EDDIE SAYS
Remember the long line that runs through the centre of the circle is called the diameter. To find the radius, we have to halve the diameter which results in a total of 32cm.
• Question 5

Look at the circle.

What is the length of the diameter? EDDIE SAYS
If we know the radius is 97m, we have to double it in order to find the total length of the diameter. 97 x 2 = 194m
• Question 6

Look at this circle.

What is the circumference?

The formulae is (2 x x r)

Remember = 3.14 81.64 cm
EDDIE SAYS
To calculate the circumference of the circle, we have to do the following calculation: (2 x 3.14 x 13) = (6.28 x 13) = 81.64cm Great focus, you're past halfway!
• Question 7

Look at this circle.

What is the circumference?

The formulae is (2 x x r)

Remember = 3.14 94.2 cm
EDDIE SAYS
This time, to calculate the circumference, we had to do the following sum: (2 x 3.14 x 15) (6.28 x 15) = 94.2cm
• Question 8

Look at this circle.

What is the circumference?

The formulae is (2 x x r)

Remember = 3.14 EDDIE SAYS
It is tricky to find the circumference of a circle from scratch! The calculation needed was; (2 x 3.14 x 4) = 25.12cm That was a tricky one, don't worry if you didn't get it right!
• Question 9

Look at this circle.

The diameter is 6m.

What is the circumference?

The formulae is (2 x x r)

Remember = 3.14 EDDIE SAYS
Again, you had the challenge of finding the circumference of a circle from scratch! This time you first needed to halve the diameter of 6m to find the radius of 3m. The calculation needed was: (2 x 3.14 x 3) = 18.84m Practise makes perfect! That’s another activity ticked off!
• Question 10

Look at this circle.

What is the circumference?

The formulae is (2 x x r)

Remember = 3.14 100.48cm
100.48
EDDIE SAYS
This time, you had to do all of the hard work! The calculation needed was: (2 x 3.14 x 16) = 100.48cm
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