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Ex 10.1, 4 Find the area of a triangle two sides of which are 18 cm and 10 cm and the perimeter is 42 cm. 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 Given a = 18 cm, b = 10 cm and Perimeter = 42 cm Semi-Perimeter = s =Perimeter/2 s = 42/2 s = 21 cm We need to find c Now, Perimeter = 42cm a + b + c = 42 cm 18 cm + 10 cm + c = 42 cm 28 cm + c = 42 cm c = 42 28 cm c = 14 cm Area of triangle = ( ( )( )( )) Putting a = 18 cm, b =10 cm, c = 14 cm & s = 21 cm Area of triangle = (21(21 18)(21 10)(21 14)) = (21(3)(11)(7)) = (21 (7 3)(11)) = (21 (21)(11)) = ("21 21" ) 11 = ("21" 2) 11 = (21) 11 = 21 11 Thus , Area = 21 11 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.