A solid metal frustum with end radii 16 cm and 8 cm and height 12 cm is melted and recast into a solid cylinder of base radius 8 cm. Find the height of the cylinder.

Question

Accepted Answer

28 cm. Frustum volume = 1/3\π × 12 × (256 + 64 + 128) = 4\π × 448 = 1792\π cm³. Cylinder: \π × 8^2 × H = 1792\π , so H = 1792/64 = 28 cm. 20 cm drops the Rr term; 84 cm forgets the 1/3 ; 112 cm halves 8 cm as though it were a diameter.

A solid metal frustum with end radii 16 cm and 8 cm and height 12 cm is melted and recast into a solid cylinder of base radius 8 cm. Find the height of the cylinder.

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