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Question
The radius of two circles are in the ratio 3 : 5, find the ratio between their circumferences.
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Solution
The ratio of the radius of the circles = 3 : 5
Let the radius of the first circle = 3x
and radius of the second circle = 5x
∴ Circumference of the first circle = 2πr
= 2π × 3x = 6πx
and circumference of the second circle = 2πr
= 2π × 5x = 10x
∴ The ratio between their circumference
= 6πx : 10πx
= 6 : 10
= 3 : 5
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