If the whole diameter of sphere is 6 inch(means radius is 3 inch) & thickness of material is 1 inch, so the radius of the hollow part should be 2 inch (3-1=2)
The total volume of the ball will be;
= Total volume - Volume of hollow part
= 4/3πr³ - 4/3πr³
= 4/3 × 3.14 × (3)³ - 4/3×3.14×(2)³
= 4 × 3.14 × 9 - 4/3 × 3.14 × 8
= 113.04 - 33.52
= 79.52
If the density of the material is 3.25 g/in3, then the density of 79.52 inch³ should be;
= 79.52 × 3.25
= 258.44 g
Now, if there are 8 spheres in one box, the weight if box will be;
= 258.44 × 8
= 2,067.52 g
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Ahh! Finally done with this, if you have any doubt just do ask me :)