1. Circumference of a Circle
Learning Objective: to be able to calculate the circumference of a circle from its radius or its diameter

2. Match the Perimeter to the Shapes
Delta
4cm
8cm
Perimeter A
32cm B
21cm C
26cm D
29cm E
22cm F
24cm G
25cm
Square
8cm
Equilateral Triangle
7cm
Kite
8cm
3cm
Trapezium
7.5cm
1.5cm
10cm
Isosceles Triangle
10cm
5cm
Parallelogram
8cm
5cm

3. Create a Table in your Exercise Books
The perimeter of a circle is called the circumference.
Measuring Circles
Circle
Circumference
Diameter
Circumference ÷ Diameter

4. Approximation of the Circumference of a Circle

5. The Circumference of a Circle
The circumference is always a multiple of the diameter.
The number is always the same:
It is called Pi and we write it as .
The number goes on forever after the decimal point.
We normally round it to 3.14.
It is on your calculator and is more accurate there.
Calculate
using

6. What is the Circumference of these Circles?
7mm
100m

7. Work out the PerimetersA B 2m
4cm
10cm C
15cm D 8m
17m F
47mm E G
12m
18m H 8m

8. Basketball Court
Mr McTernan and Mr Océan have been asked to lay out a new basketball court with tape.
Tape comes in rolls of 20m.
How many rolls do they need to order?
Assuming they make no errors, how much tape will be left over?
All measurements are in metres.