1.5 Measurement AS 91030

Area of Circles I can find the area of a circle Learning objectives 20 May 2019 I can find the area of a circle I can find the area of part of a circle I can find the area of an annulus I can find the radius when I know the area

Area of Circles The rule you need to use is Area = Πr² (Π x radius x radius) when the radius = 12 cm Area = Π x 12² (Π x 12 x 12) = 452cm²

Parts of circles The rule you need to use is Area = Πr² (Π x radius x radius) but now we only have half a circle! Area = Πr²÷ 2 when the radius = 4m Area = Πx4²÷ 2 = 25 m²

The rule you need to use is Area = Πr² (Π x radius x radius) but now we only have part of a circle! Area = 3 4 Πr² when the radius = 6m Area = 3 4 πx6² = 84.8 m²

The rule you need to use is Area = Πr² (Π x radius x radius) but now we only have part of a circle! Area = 200 360 Πr² when the diameter = 8m Area = 200 360 πx4² = 27.9 m² 200°

Annulus area = 𝜋 x 8² - 𝜋 x 3² = 173 cm² Think donuts! 8 cm To find the area of the pink section Find the area of the big circle Find the area of the small circle do a subtraction 3cm area = 𝜋 x 8² - 𝜋 x 3² = 173 cm²

I can find the radius when I know the area The rule you need to use is Area = Πr² (Π x radius x radius) when the area = 150 cm² 150 = 𝜋𝑟² 𝑟² = 150 𝜋 r = 150 𝜋 r = 6.9 cm

Success Criteria I can find the area of a circle I can find the area of part of a circle I can find the area of an annulus I can find the radius when I know the area