2. Starter Calculate the Circumference of each of these shapes. Remember that in any circle: Circumference = π x Diameter or C = πd or C = 2πr a)b)c) 10cm 8cm 4cm

3. Area of a Circle We have looked at the Area of various shapes over the last few lessons We have also looked at finding the area of ‘compound shapes’ Today we are going to be focusing on circles We will be learning a new formula

4. Area of a Circle Learning Objectives All will be able to use the formula to work out the Area of circles (Level 6) Most will be able to calculate the areas of semi-circles and quarter-circles (Level 6/7) Some will be able to apply these formulae to practical questions (Level 6/7) Demonstration of the Area of a Circle formula

5. Area of a Circle The area of a circle is given by the following formula… A = πr 2 A = Area π = ‘pi’ = 3.14…… (on calculator) r = radius of the circle Area (A) Radius (r)

6. Area of a Circle Example Question a)A circle has a radius of 6cm. Calculate its Area. 6cm Area A = πr 2 A = π x 6 2 A = 113.10cm 2 (2dp)

7. Area of a Circle Example Question b)A circle has a diameter of 9cm. Calculate its Area. 9cm Area A = πr 2 A = π x 4.5 2 A = 63.62cm 2 (2dp)

8. Area of a Circle Example Question c)Calculate the Area of this semicircle… 8m Area A = πr 2 A = π x 8 2 A = 201.06m 2 (2dp) Then divide by 2  201.06 ÷ 2 = 100.53m 2 16m

9. Area of a Circle Example Question d)How would you work out the area of this shape, made from a square and 4 semi-circles? 8cm The Square 8 x 8= 64 cm 2 The 4 semi-circles  You can imagine opposite sides could be pushed together to make a full circle A = πr 2 A = π x 4 2 A = 50.27 cm 2 A = 100.53 cm 2 Total  64 + 100.53= 164.53 cm 2 Radius = 4 Double (2 circles in total)

10. Summary We have learnt another formula involving circles We have looked at working out the Area of a Circle We have seen a variety of different problems on this topic