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4 Sectors The Area of a Circle Transform

8 Sectors The Area of a Circle Transform

16 Sectors The Area of a Circle Transform

A = πr x r = πr2 πr ½C ? r 32 Sectors As the number of sectors  , the transformed shape becomes more and more like a rectangle. What will the dimensions eventually become? 32 Sectors Remember C = 2πr Transform πr ½C r A = πr x r = πr2

The Area of a Circle A = r2 1 2 Find the area of the following circles. 1 2 8 cm 9.5 cm A = r2 A =  x 82 A = 201.1 cm2 (1 dp) A = r2 A =  x 9.52 A = 283.5 cm2 (1 dp)

The Area of a Circle A = r2 3 4 Find the area of the following circles. 6 mm 3 2.4 m 4 A = r2 A =  x 32 A = 28.3 mm2 (1 dp) A = r2 A =  x 1.22 A = 4.5 m2 (1 dp)

A = r2 Find the area of the clock face and radar screen. 12 cm 60 cm A =  x 122 A = 452.4 cm2 (1 dp) A = r2 A =  x 302 A = 2827 cm2 (nearest cm2)

The Area of a Circle A = r2 1 2 Find the area of the following semi-circles. 1 2 8 cm 9.5 cm A = ½r2 = ½ x  x 42 = 25.1 cm2 (1 dp) A = ½r2 = ½ x  x 4.752 = 35.4 cm2 (1 dp)

The Area of a Circle A = r2 3 4 Find the area of the ¼ and ¾ circles. 6 cm 8.5 cm A = r2 A = ¼r2 = ¼ x  x 62 = 28.3 cm2 (1 dp) A = ¾r2 = ¾ x  x 8.52 = 170.2 cm2 (1 dp)

The Area of a Circle A = r2 6 5 Find the radius/diameter of the following circles. A = 25 cm2 find the diameter. 6 5 A = 30 cm2 find the radius. r2 = 25 r2 = 25/ r = (25/) r = 2.82 d = 2 x 2.82 = 5.6 cm 1dp r2 = 30 r2 = 30/ r = (30/) r = 3.1 cm 1dp