If the radius of a sphere is tripled, then what will be the ratio of the surface area of original sphere to that of the new sphere?

If the radius of a sphere is tripled, then what will be the ratio of the surface area of original sphere to that of the new sphere? Correct Answer 1:9

Let the original radius = r Original surface area = 4 πr2 According to the question, New radius = 3r New surface area = 4 π (3r)2 = 36 πr2 Ratio = original surface area / new surface area = 4 πr2 / 36 πr2 = 1:9
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