Example 14 - Chapter 9 Class 7 Perimeter and Area

Transcript

Example 14 The adjoining figure shows two circles with same centre. The radius of the larger circle is 10 cm and the radius of the smaller circle is 4 cm. Find: (a) the area of the larger circle Radius of larger circle = R = 10 cm Area of larger circle = 𝜋R2 = 3.14 × (10)2 = 3.14 × 100 = 314/100 × 100 = 314 cm2 ∴ Area of larger circle is 314 cm2 Example 14 (b) the area of the smaller circle Radius of smaller circle = r = 4 cm Area of smaller circle = 𝜋r2 = 3.1 (4)2 = 3.14 × 16 = 314/100 × 16 = 5024/100 = 50.24 cm2 ∴ Area of smaller circle is 50.24 cm2 Example 14 (c) the shaded area between the two circles. (π = 3.14) Shaded area = Area of larger circle − Area of smaller circle = 314 − 50.24 = 314 − 50.24/100 = (314 × 100 − 5024)/100 = (𝟑𝟏𝟒𝟎𝟎 − 𝟓𝟎𝟐𝟒)/𝟏𝟎𝟎 = 26376/100 = 263.76 cm2 ∴ Shaded area is 263.76 cm2