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The base of an isosceles triangle is 24 cm and its area is 192 sq. cm. Find its perimeter. - Mathematics

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Question

The base of an isosceles triangle is 24 cm and its area is 192 sq. cm. Find its perimeter.

Sum
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Solution

It is given that

Area = 192 sq.cm

base = 24 cm

Knowing the length of the equal side, a and base, b of an isosceles triangle, the area can be calculated using the formula,

A = `1/4 xx b xx sqrt (4a^2 - b^2`     

Let 'a' be the length of an equal side.

Area = `1/4 xx b xx sqrt(4a^2 - b^2)`   

192 = `1/4 xx 24 xx sqrt(4a^2 - 576)` 

192 = `6 sqrt(4a^2 - 576)` 

`sqrt(4a^2 - 576` = 32

4a2 – 576 = (32)2

4a2 – 576 = 1024

4a2 = 1024 + 576

4a2 = 1600

a = 20 cm

Hence, perimeter = 20 + 20 + 24

= 64 cm

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Chapter 20: Area and Perimeter of Plane Figures - Exercise 20 (A) [Page 247]

APPEARS IN

Selina Concise Mathematics [English] Class 9 ICSE
Chapter 20 Area and Perimeter of Plane Figures
Exercise 20 (A) | Q 6 | Page 247
Nootan Mathematics [English] Class 9 ICSE
Chapter 16 Mensuration
Exercise 16A | Q 12. | Page 315
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