Henry Ernest Dudeney/Puzzles and Curious Problems/69 - The Four Cyclists

by : $69$

 * The Four Cyclists
 * The four circles represent cinder paths.


 * Dudeney-Puzzles-and-Curious-Problems-69.png


 * The four cyclists started at noon.
 * Each person rode round a different circle,
 * one at the rate of $6$ miles an hour,
 * another at the rate of $9$ miles an hour,
 * another at the rate of $12$ miles an hour,
 * and the fourth at the rate of $15$ miles an hour.
 * They agreed to ride until all met at the centre, from which they started, for the fourth time.
 * The distances around each circle was exactly one-third of a mile.
 * When did they finish their ride?