1. Circles
OCR Stage 6

2. Circumference
radius is diameter ÷ 2
radius
diameter
Tangent

3. Circumference of Circle
Formula
Circumference, C =
d is the diameter d
on Calculator?
SHIFT
EXP =

4. 3
C =
X 3
= …..
= 9.42cm
C =
X 7
= ….. 7
= 22.0cm
Diameter = 2 x radius
= 8 4
C =
x 8
= …
= 25.1cm

5. If you know the circumference?
You can calculate the Radius!
38cm
π X d
= 38cm
d = 38 ÷ π =
= 12.1cm
14cm
π X d
= 14cm
d = 14 ÷ π =
= 4.5cm
π X d
23cm
= 23cm
d = 23 ÷ π =
r = d ÷ 2
= ÷ 2 =
r = 3.7cm

6. Area of Circle

7. Area of Circle
Formula
Area, A = r
on Calculator?
SHIFT
EXP =

8. 3
A =
X 32
= …..
= 28.3cm2
A =
X 72
= ….. 7
= 153.9cm2
Radius = diameter / 2
= 8 16
A =
x 82
= …
= 201.1cm2