1. Circles By
Freddie
And
Liam

2. Radius and Diameter Radius is ALWAYS half the diameter.
Diameter is ALWAYS
double the radius
1) If the diameter of a circle is 100cm what
length is the radius?
2) If the radius is 64cm what is the length
of the diameter?

3. Solutions 1) 2) Diameter = 100cm Radius = ½ Diameter ½ of 100 = 50
Radius = 50cm
100 cm
64cm 2)
Radius = 64cm
Diameter = 2 x radius
2x64 = 128
Radius

4. Circumference
The circumference is the distance around the edge of a circle approximately 3x the Diameter

5. How do you find the circumference?
We use something called pi to help us get an accurate measuring of the circumference Pi can be easily recognised by the sign: π To find the circumference we use the formula: C = πD This means circumference = Pi multiplied by diameter Pi is = to 100 digits Or 3.14 for short

6. Circumference question
(answer to 2 DP)
Diameter =10cm
C=πD
=π x 10
= 31.42
10cm

7. How do you find the area?
To find the area of a circle, again you use Pi (π) or Although this time it’s a little more complicated. The first step is A = πr2 This means area = 3.14 * Radius2

8. If the diameter is 7cm, work out the area.
Area Question
If the diameter is 7cm, work out the area.
7cm

9. Solutions
A=πr2 =π*(3.52) =38.48

10. Basically just remember this: