Shape and Space - part 1
CIRCUMFERENCE 1: THE BASICS
LEVEL 2
The diameter of a circle is the

distance across it through the centre.


The radius is the distance from
the centre to the edge.
The circumference is the distance 
around the edge of the circle

Finding the circumference
If you measure the diameter of any circle, then measure around the
circumference, you’ll find that the circumference is just over 3 times
bigger than the diameter.
22cm
Try checking this with a
measuring tape
This number, the number of times
the diameter is multiplied by to find
the circumference, has the name π
- (a Greek letter pronounced like
‘pie’)
7cm

f l ex i p
π is usually given the value 3.14 or
3.142 but if you press the EXP button
on a scientific calculator, you’ll see a
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Shape and Space - part 1
more accurate value (in fact it goes on
forever).
So to find the distance round the edge of any circle, multiply the
diameter by π.
The formula is:
C =πd


circumference
diameter
(The multiplication sign is not used in formulae, so C = π d means
C = π x d)
Example:
The circular pond is 4m wide. What is the distance around the edge?
Take the value π = 3.14
C
=
=
=
πd
3.14 x 4 m
12.56m
4m
A)
Try these using the value π = 3.14
1)
Find the circumference of these circles:
a)
b)
2cm
c)
d)
5cm
7cm
9cm
A circular teepee tent is 3m across the base. What is it’s
circumference?
3)
A vinyl LP record has a diameter of 30cm. What is the distance
around the edge?
f l ex i p
2)
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Shape and Space - part 1
4)
A hula hoop is 90cm across. What length of plastic is needed to
make it?
5)
Anne is completing an order for birthday cakes. How much
ribbon is needed to go round a cake 25cm wide?
6)
A circular rug is 95cm across. What length of binding is needed
to go round the edge?
π may be given as
22
7
(3
1
7
). In this case, work out the value as a
fraction and cancel if possible
Example:
22
Find the circumference of this circle, using the value π = 7
3
22
x 21 (cancel by 7)
7
1
21cm
= 22 x 3 cm
= 66cm
B)
More questions
Find the circumference using the value π =
1)
2)
f l ex i p
49cm
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3)
4)
35m
14m
3
22
7
105m
Shape and Space - part 1
Radius and diameter
Sometimes you may be given the radius instead of the diameter.
d
r
To find the diameter, just multiply the radius by 2
C =πd
C)
Try these questions using the value π = 3.142
1)
Find the circumference of these circles:
a)
b)
c)
4m
2)
6m
7m
The minute hand on a clock reaches to the edge, and is 5cm long.
What distance does the tip of the hand travel in an hour?
5cm
3)
A cow is tethered on the end of a rope 10m long, attached to a
fixed post. How far can she walk round in a circle?
f l ex i p
10m
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Shape and Space - part 1
Answers
Circles - Circumference A
A)
1)
a) 6.28cm
2)
9.42m
3)
94.2cm
4)
282.6cm
5)
78.5cm
6)
298.3cm
b) 15.7cm
c) 21.98cm
b) 37.704m
c) 43.988m
B)
1)
154cm
2)
44m
3)
110m
4)
330m
C)
a) 25.136m
2)
31.42cm
3)
62.84m
f l ex i p
1)
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d) 28.26cm