A CD that is 0.75 mm thick has outer diameter of 128 mm and inner diameter of 15 mm.The volume of the CD is A)1920 mm³. B)5300 mm³. C)9520 mm³. D)38079 mm³.

Question

Quizplus · Accepted Answer

The volume of the CD can be calculated by subtracting the volume of the hole in the center from the volume of the entire disc. The volume of the entire disc is the volume of a cylinder with height 0.75 mm and radius 64.5 mm (the average of the outer and inner radii):
V1 = πr^2h = π(64.5)^2(0.75) ≈ 9520 mm^3

The volume of the hole in the center is the volume of a cylinder with height 0.75 mm and radius 7.5 mm (the difference between the outer and inner radii):
V2 = πr^2h = π(7.5)^2(0.75) ≈ 133 mm^3

Therefore, the volume of the CD is:
V1 - V2 ≈ 9387 mm^3, which is closest to option C, 9520 mm^3.

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