# mathematics

A spherical ball weighs three times as much as another ball of identical appearance and composition. The second ball weighs less because it is actually hollow inside. Find the radius of the hollow cavity in the second ball, given that each ball has a 5-inch radius.

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1. since they have the same density, we have to worry about is the volume, since it is in the same ratio as the weight.
If the outside radius is R and the inside radius of the cavity is r, then you have
4/3 π * R^3 = 3 * 4/3 π(R^3 - r^3)
now solve for r.

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oobleck

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