Explanation:
the answer is simply the volume of the whole model minus the volume of the core ball.
the volume of a sphere (ball, ...) is
4/3 × pi×r³
the radius is always half of the diameter.
radius of the whole model = 18/2 = 9 in.
radius of the core ball = 3/2 = 1.5 in.
so, we have as volume of the clay
4/3 × 3.14 × 9³ - 4/3 × 3.14 × 1.5³ =
= 4/3 × 3.14 × (9³ - 1.5³) = 4/3 × 3.14 × (729 - 3.375) =
= 4/3 × 3.14 × 725.625 = 3,037.95 in³