Question

The ratio of the radii of two circles is 5:3.find the ratio of their circumfrences.

Answer 1

let the radii be 5x and 3x

circumference of first circle = 2 pi(5x)
circumference of the second circle
=2 pi (3x)

ratio = 2 pi (5x) /2 pi (3x)
= 5/3

Answer 2

Lets take radii of one circle ,r = 5 x
radii of the second circle , R = 3 x

Circumference of the first circle = 2πr = 2π × 5x
                                                  = 10πx
Circumference of the second circle = 2πR = 2π × 3x
                                                        = 6πx

Therefore , ratio of the circumference of the two circles = 10πx ÷  6πx
                                                                                      = 10 ÷ 6
                                                                                      = 5 ÷ 3 
                                                                                      = 5 : 3