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Ex 12.2, 9 - A brooch is made with silver wire in form of - Ex 12.2

  1. Chapter 12 Class 10 Areas related to Circles
  2. Serial order wise
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Ex 12.2, 9 A brooch is made with silver wire in the form of a circle with diameter 35 mm. The wire is also used in making 5 diameters which divide the circle into 10 equal sectors as shown in figure. Find : the total length of the silver wire required Here, Brooch is made with silver wire in the form of a circle. Diameter of the brooch = 35 mm Radius of brooch = 35/2 mm Since wire is used in making 5 diameter & circle. So, Total wire is used = length of wire in circle + Wire used in 5 diameters Length of wire in circle Length of wire in circle = circumference of circle = 2๐œ‹๐‘Ÿ = 2ร—22/7ร—35/2 = 22 ร— 5 = 110 mm Silver wire used in 5 diameters = 5 ร— Diameter of circle = 5 ร— 35 = 175 mm Now, Total wire is used = length of wire in circle + Wire used in 5 diameters = 110 + 175 = 285 mm Ex 12.2, 9 A brooch is made with silver wire in the form of a circle with diameter 35 mm. The wire is also used in making 5 diameters which divide the circle into 10 equal sectors as shown in figure. Find : (ii) the area of each sector of the brooch. Since the wire divides the circle into 10 equal sectors Area of each sector of the brooch = 1/10ร— Area of all sectors of the brooch Area of all sectors of the brooch = area of circle = ๐œ‹๐‘Ÿ2 = 22/7ร—(35/2)^2 = 22/7ร—35/2ร—35/2 = (11 ร— 5 ร— 35)/2 Area of each sector of the brooch = 1/10ร— Area of all sectors of the brooch = 1/10ร—(11 ร— 5 ร— 35)/2 = 385/4 mm2 โˆด Area of each sector = 385/4 mm2

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