A wooden thread spool is a cylinder of radius 2.8 cm and length 12 cm with a cone of the same radius and depth 4.5 cm hollowed out of each flat end. Find the volume of wood in the spool, in cubic centimetres. (Take π = 22/7.)

Question

Accepted Answer

221.76. Base area \π r^2 = 22/7(7.84) = 24.64 cm². Cylinder = 24.64 × 12 = 295.68 cm³. Each cone = 1/3(24.64)(4.5) = 36.96 cm³, so both = 73.92 cm³. Wood = 295.68 − 73.92 = 221.76 cm³. 258.72 removes only one cone; 369.6 adds the cones instead of subtracting them; 73.92 is the wood taken out, not the wood left.

A wooden thread spool is a cylinder of radius 2.8 cm and length 12 cm with a cone of the same radius and depth 4.5 cm hollowed out of each flat end. Find the volume of wood in the spool, in cubic centimetres. (Take π = 22/7.)

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