Henry Ernest Dudeney/Puzzles and Curious Problems/244 - Sharing a Grindstone

by : $244$

 * Sharing a Grindstone
 * Three men bought a grindstone $20$ inches in diameter.
 * How much must each grind off so as to share the stone equally,
 * making an allowance of $4$ inches off the diameter as waste for the aperture?
 * We are not concerned with the unequal value of the shares for practical use --
 * only with the actual equal quantity of stone each receives.