U7: Circles

Key Learning Points:

• The diameter of a circle is a straight line that starts from one point on the circle's perimeter, cutting through the centre of the circle and reaching the other point on the perimeter.
• The radius is a straight line drawn from the centre of the circle to the perimeter of the circle
• Thus 2 x radius = diameter
• Circumference is the perimeter of a circle
• Circumference = 'pi' x diameter or 'pi' x (2 x radius)
• 'pi' is generally taken to be 22/7 or 3.14 (questions will tell you which 'pi' to use)
• Area of a Circle = 'pi' x radius x radius

Generally, be careful with the units in this topic and if possible, try to use 'pi' as 22/7 as it is neater and does not contain decimals.