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Find the area of a triangle two sides of which are 18 cm and 10 cm and the perimeter is 42 cm. - CBSE Class 9 - Mathematics

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Question

Find the area of a triangle two sides of which are 18 cm and 10 cm and the perimeter is 42 cm.

Solution

Let the third side of the triangle be x.

Perimeter of the given triangle = 42 cm

18 cm + 10 cm + = 42

x = 14 cm

`s = "Perimeter"/2=42/2=21cm`

By Heron's formula,

`"Area of a triangle "=sqrt(s(s-a)(s-b)(s-c))`

`"Area of the given triangle "=(sqrt(21(21-18)(21-10)(21-14)))cm^2`

                                         `=(sqrt(21(3)(11)(7)))cm^2`

                                        `= 21sqrt11 cm^2`

 

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APPEARS IN

 NCERT Solution for Mathematics Class 9 (2018 to Current)
Chapter 12: Heron's Formula
Ex. 12.10 | Q: 4 | Page no. 203

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Solution Find the area of a triangle two sides of which are 18 cm and 10 cm and the perimeter is 42 cm. Concept: Area of a Triangle by Heron’S Formula.
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