Question

The radii of two circles are in the ratio 3 : 5, find the ratio between their
circumferences.
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Answer 1

The ratio of the radii of the circles = 3 : 5

Let radius of the first circle = 3x

and radius of second circle = 5x

∴ Circumference of first circle = 2πr

= 2π x 3x = 6πx

and circumference of second circle = 2πr

= 2π x 5x = 10πx

∴ Ratio between their circumferences

= 6πx : 10πx

= 16 :10

= 3 : 5

Answer 2

Answer:

let the ratio be 3x and 5x

Circumference of ratio = 2r

= 2 × 22/7 × 3x

= 132/7 x

Circumference of ratio = 2r

2× 22/7× 5x = 220/7x

Ratio between them =

132/7x : 220/7x

= 132 x 7x

_____ _____

7x 220

= 3/5

= 3:5 answer

Hope it is useful for you.