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Question -

An iron spherical ball has been melted and recast into smaller balls of equal size. If the radius of each of the smaller balls is 1/4 of the radius of the original ball, how many such balls are made? Compare the surface area, of all the smaller balls combined together with that of the original ball.



Answer -

Let the radius of thebig ball be x cm

The, the radius of thesmall ball = x/4 cm

And, let the number ofballs = n

Then according to thequestion, we have

Volume of n smallballs = Volume of the big ball

n x 4/3 π(x/4)3 =4/3 πx3

n x (x3/64) = x3

n = 64

Therefore, the numberof small balls = 64

Next,

Surface area of allsmall balls/ surface area of big ball = 64 x 4π(x/4)2/ 4π(x)2

= 64/16 = 4/1

Thus, the ratio of thesurface area of the small balls to that of the original ball is 4:1

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