# 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 from 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 the other.

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:

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.

Which letter shows the circumference?

Look at this circle.

Which letter shows the diameter?

Look at the circle.

Look at the circle.

Can you type the name of the line labelled 'c'?

Look at the circle.

Can you type the name of the line labelled 'b'?

Look at this circle.

The radius is 16cm. What is the diameter?

Look at this circle.

The diameter is 96m. What's the radius?

Look at this circle.

What is the circumference?

The formulae is (2 x  x r)

Remember  = 3.14

30.4 cm

31.04 cm

32.4 cm

31.4 cm

Look at this circle.

The diameter is 22cm.

What is the circumference?

The formulae is (2 x  x r)

Remember  = 3.14

Look at this circle.

What is the circumference?

The formulae is (2 x  x r)

Remember  = 3.14

• Question 1

Look at this circle.

Which letter shows the circumference?

c
C
EDDIE SAYS
The letter C shows the circumference as it is the measurement all the way around the circle.
• Question 2

Look at this circle.

Which letter shows the diameter?

C
c
EDDIE SAYS
This time, letter C represents 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.

B
b
EDDIE SAYS
Did you find it? The radius is labelled as b. 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.

Can you type the name of the line labelled 'c'?

Diameter
The diameter
EDDIE SAYS
Remember the long line that runs through the centre of the circle is called the diameter! Are you feeling more confident?
• Question 5

Look at the circle.

Can you type the name of the line labelled 'b'?

EDDIE SAYS
Remember the line that runs from the centre of the circle to the edge of the circle is called the radius.
• Question 6

Look at this circle.

The radius is 16cm. What is the diameter?

EDDIE SAYS
The diameter is 32cm in length as it's double the length of the radius! 16 x 2 = 32
• Question 7

Look at this circle.

The diameter is 96m. What's the radius?

EDDIE SAYS
The radius is 48m in length as it's half the length of the radius. 96/2 = 48
• Question 8

Look at this circle.

What is the circumference?

The formulae is (2 x  x r)

Remember  = 3.14

31.4 cm
EDDIE SAYS
It's tricky to find the circumference of a circle! The calculation needed was: (2 x 3.14 x 5) = 31.4cm
• Question 9

Look at this circle.

The diameter is 22cm.

What is the circumference?

The formulae is (2 x  x r)

Remember  = 3.14

EDDIE SAYS
This time you first needed to halve the diameter of 22cm to find the radius of 11cm. The calculation needed was: (2 x 3.14 x 11) = 69.08cm Hopefully, by now you're feeling more confident.
• Question 10

Look at this circle.

What is the circumference?

The formulae is (2 x  x r)

Remember  = 3.14

87.92
EDDIE SAYS
This time, you had to do all of the hard work! The calculation needed was: (2 x 3.14 x 14) = 87.92cm Great work, you've completed another activity! How about attempting another one so you feel super confident?
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