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Ex 9.2, 10 From a circular card sheet of radius 14 cm, two circles of radius 3.5 cm and a rectangle of length 3 cm and breadth 1cm are removed. (as shown in the adjoining figure). Find the area of the remaining sheet. (𝑇𝑎𝑘𝑒 𝜋=22/7) Remaining Area = Area of larger circle − 2 × Area of smaller circle − Area of rectangle Area of larger circle Radius of larger circle = R = 14 cm Area of larger circle = 𝜋R2 = 𝟐𝟐/𝟕 × (14)2 = 22/7 × 14 × 14 = 22/1 × 2 × 14 = 44 × 14 = 616 cm2 Area of smaller circle Radius of smaller circle = r = 3.5 cm Area of smaller circle = 𝜋r2 = 𝟐𝟐/𝟕 × (3.5)2 = 22/7 × (35/10)^2 = 22/1 × (7/2)^2 = 𝟐𝟐/𝟕 × 𝟕/𝟐 × 𝟕/𝟐 = 11/7 × 7/1 × 7/2 = 22/7 × 1 × 7/2 Area of rectangle Length of rectangle = l = 3 cm Breadth of rectangle = b = 1 cm Area of rectangle = l × b = 3 × 1 = 3 cm2 Therefore, ∴ Remaining Area = Area of larger circle − 2 × Area of smaller circle − Area of rectangle = 616 − 2 × (𝟕𝟕/𝟐) − 3 = 616 − 77 − 3 = 616 − 80 = 536 cm2 ∴ Required area is 536 cm2

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Davneet Singh

Davneet Singh has done his B.Tech from Indian Institute of Technology, Kanpur. He has been teaching from the past 14 years. He provides courses for Maths, Science, Social Science, Physics, Chemistry, Computer Science at Teachoo.