3. A circle is a 2-dimensional shape
which made by drawing a curve
that has always the same distance
from the center. It is one of the
basic shape in geometry

4. Circumference: The distance around the circle; a
special name for the perimeter of a circle
 Arc: A part of the circumference
 Radius: The distance from the centre to the
circumference
 Diameter: the distance from side to side passing
though the centre; the greatest with of a circle


6. The formula: A = π × r2
Π=
*It is very important to know either the Radius or
the Diameter in order to take out the area of a
circle*

7. Ex 1
Ex 2
r=4cm
d=6cm
So, r=3cm
A = π × r2
A=
x 42
A = π × r2
A=
A=
x 32
x 16 ~ 5.28
A=
x 9 ~ 28.28

9. To find an area of an Irregular shape,
Separate each shape to find its area
Example
A sports ground
Rectangle
A=wxh, so 60×40=2400m2
Circle
d=40m, so r=20m
A=πr2=π×202=400π=1256m2
Irregular Shape
2400m2+1256m2=3656m2
40m
60m
40m
Note
π=3.14
d÷2=r
A=πr2=πxr2
A=wh=wxh
40m
60m

10. Thank you