Circles Formulas Circumference = π * diameter C = πd Area = π * r2

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Presentation transcript:

Circles Formulas Circumference = π * diameter C = πd Area = π * r2 A = πr2 When working with circles make sure you have the diameter and radius.

Find the circumference and area of the circle below 8cm Radius = Diameter = 8 16 C = πd A = πr2 C = π*16 A = π*82 C = 50.24cm A = 64π = 200.96cm2

A circle has a diameter of 12π units. What is it’s area? (express in π units) Diameter = Radius = 12π 6π A = πr2 A = π*(6π)2 A = 36π2*π = 36π3units2

What is the area of the shaded region? 20cm Diameter = Radius = 20cm 10cm A(square) = 20 * 20 = 400cm2 A(circle) = πr2 = π*(10)2 = 100π = 314cm2 A (shaded) = 400 - 314 = 86cm2

What is the area of a circle that has a circumference of 94.2cm C = πd A = πr2 94.2 = πd A = π(15)2 94.2 = d π A = 225π A = 706.5cm2 d = 30cm r = 15cm

What is the circumference of a circle that has an area of 452.16cm2 C = πd 452.16 = πr2 C = π*24 452.16 = r2 π C = 75.36cm r2 = 144cm r = 12cm d = 24cm