Henry Ernest Dudeney/Modern Puzzles/191 - Crossing the Ferry/Solution

by : $191$

 * Crossing the Ferry

Solution
First let us establish who we have here, and assign them labels, according to seniority and gender:


 * $(1): \quad$ Mrs. Webster's mother and her husband: let them be labelled $A$ and $X$ (Adrienne and Xavier)
 * $(2): \quad$ Mr. Webster and his wife Mrs. Webster: let them be labelled $B$ and $Y$ (Bertram and Yvonne)
 * $(3): \quad$ Mr. and Mrs. Webster's son and his wife: let them be labelled $C$ and $Z$ (Colin and Zoe)

Hence the rules state:
 * $B$ cannot share a boat, or remain together on the same side as either $A$ or $C$.
 * $Y$ cannot share a boat, or remain together on the same side as either $X$ or $Z$.
 * Men must not be outnumbered by women at any stage.

Here they are at each stage of the crossing, where the bullet indicates where the boat is:


 * $\begin {array} {r c| c l}

A B C \ X Y Z & \bullet & & \\ A C \ X Z & & \bullet & B \ Y \\ A C \ X Y Z & \bullet & & B\\ A C \ Y & & \bullet & B \ X Z \\ A B C \ Y & \bullet & & X Z \\ B \ Y & & \bullet & A C \ X Z \\ B \ Y Z & \bullet & & A C \ X \\ Y & & \bullet & A B C \ X Z \\ B Y & \bullet & & A C \ X Z \\ & & \bullet & A B C \ X Y Z \end{array}$