# Ex 12.1, 6

Last updated at May 29, 2018 by Teachoo

Last updated at May 29, 2018 by Teachoo

Transcript

Ex 12.1, 6 An isosceles triangle has perimeter 30 cm and each of the equal sides is 12 cm. Find the area of the 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 Given triangle is isosceles In isosceles triangle, two sides are equal So, a = b = 12 cm and Perimeter = 30 cm Semi-Perimeter = s =Perimeter/2 s = 30/2 s = 15 cm We need to find c Perimeter = 30cm a + b + c = 30 cm 12 cm+ 12 cm + c = 30 cm 24 + c = 30 c = 30 24 c = 6 cm Area of triangle = ( ( )( )( )) Putting a = 12 cm, b =12 cm, c = 6 cm & s = 15 cm = (15(15 12)(15 12)(15 6)) = (15(3)(3)(9)) = (15 (9)(9)) = ("9" 9) 15 = ("92" ) 15 = (9) 15 = 9 15 Thus, Area = 9 15 cm2

Class 9

Important Questions for Exam - Class 9

- Chapter 1 Class 9 Number Systems
- Chapter 2 Class 9 Polynomials
- Chapter 3 Class 9 Coordinate Geometry
- Chapter 4 Class 9 Linear Equations in Two Variables
- Chapter 5 Class 9 Introduction to Euclid's Geometry
- Chapter 6 Class 9 Lines and Angles
- Chapter 7 Class 9 Triangles
- Chapter 8 Class 9 Quadrilaterals
- Chapter 9 Class 9 Areas of parallelograms and Triangles
- Chapter 10 Class 9 Circles
- Chapter 11 Class 9 Constructions
- Chapter 12 Class 9 Herons Formula
- Chapter 13 Class 9 Surface Areas and Volumes
- Chapter 14 Class 9 Statistics
- Chapter 15 Class 9 Probability

About the Author

Davneet Singh

Davneet Singh is a graduate from Indian Institute of Technology, Kanpur. He has been teaching from the past 8 years. He provides courses for Maths and Science at Teachoo. You can check his NCERT Solutions from Class 6 to 12.