Henry Ernest Dudeney/Modern Puzzles/163 - The Russian Motor-Cyclists

by : $163$

 * The Russian Motor-Cyclists
 * Two Russian Army motor-cyclists, on the road $A$, wish to go to $B$.
 * Now Pyotr said: "I shall go to $D$, which is $6$ miles, and then take the straight road to $B$, another $15$ miles.
 * But Sergei thought he would try the upper road by way of $C$.
 * Curiously enough, they found on reference to their odometers that the distance either way was exactly the same.


 * Dudeney-Modern-Puzzles-163.png


 * This being so, they ought to have been able easily to answer the General's simple question,
 * "How far is it from $A$ to $C$?"
 * it can be done in the head in a few moments, if you only know how.
 * Can the reader state correctly the distance?