The Radius of a Circle is 5 M. Find the Circumference of the Circle Whose Area is 49 Times the Area of the Given Circle - Mathematics

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Sum

The radius of a circle is 5 m. Find the circumference of the circle whose area is 49 times the area of the given circle.

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Solution

Area of the circle having radius 5 m is

A = π × (5)

= 25 π m2

Let r be the radius of the circle whose area is 49 times of the given circle.

π r2 = 49 × (π x 52)

r2 = (7 × 5)2

r = 35 m

Hence circumference of the circle

circumference = 2πr

circumference = 2 × `22/7`× 35

circumference = 220 m

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Chapter 20: Area and Perimeter of Plane Figures - Exercise 20 (C) [Page 261]

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Selina Concise Mathematics Class 9 ICSE
Chapter 20 Area and Perimeter of Plane Figures
Exercise 20 (C) | Q 7 | Page 261

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