Answer: 54pi cm^3 (choice A)
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Step-by-step explanation:
The radius of each sphere is r = 3
The volume of one sphere is
V = (4/3)*pi*r^3
V = (4/3)*pi*3^3
V = 36pi
That's the volume of one sphere.
Three spheres take up 3*36pi = 108pi cm^3 of space.
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The radius of the cylinder is also r = 3, since each tennis ball fits perfectly in the container.
The height is h = 18 because we have each ball with a diameter 6, which leads to the three of them stacking to 3*6 = 18.
The volume of the cylinder is...
V = pi*r^2*h
V = pi*3^2*18
V = 162pi
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Subtract the volume of the cylinder and the combined volume of the spheres: 162pi - 108pi = (162-108)pi = 54pi
This is the exact volume of empty space inside the can.
This points to choice A as the final answer