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Last updated at May 29, 2018 by Teachoo

Transcript

Ex 12.2, 6 An umbrella is made by stitching 10 triangular pieces of cloth of two different colours (see the given figure), each piece measuring 20 cm, 50 cm and 50 cm. How much cloth of each colour is required for the umbrella? There are 10 triangles, 5 triangles of blue color and 5 triangles of grey color Area of each cloth = 5 × (Area of 1 triangle) Area of triangle Area of triangle = √(s(s−a)(s−b)(s −c)) Here, s is the semi-perimeter, and a, b, c are the sides of the triangle a = 50 cm ,b = 20 cm, c = 50 cm s = (𝑎 + 𝑏 + 𝑐)/2 Area of triangle = √(𝑠(𝑠 −𝑎)(𝑠 −𝑏)(𝑠 −𝑐)) Area of triangle = √(60(60−50)(60−20)(60−50)) cm2 = √(60" × " (10)"×" (40)"×" (10)) = √((6)" ×" (4)"×" (104)) = √((6)" ×" (22)"×" (104)) = √6 ×√22× √104 = √6 ×2× 102 = 200 √6 cm2 Thus , Area of triangle = 200√6 cm2 Area of each cloth required = 5 × Area of triangle = (5 × 200√6) cm2 = 1000√6 cm2

About the Author

Davneet Singh

Davneet Singh is a graduate from Indian Institute of Technology, Kanpur. He has been teaching from the past 10 years. He provides courses for Maths and Science at Teachoo.