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Calculating Circle Areas and Radii - Math Tutorial

Learn how to find the area of circles and determine the radius/diameter using pi and formulas. Practice calculations in this comprehensive guide!

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Calculating Circle Areas and Radii - Math Tutorial

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  1. A =r2 The Area of a Circle 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)

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

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

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

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

  6. The Area of a Circle A =r2 Find the radius/diameter of the following circles. 6 5 A = 25 cm2 find the diameter. 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

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