Henry Ernest Dudeney/Puzzles and Curious Problems/329 - The Four Pennies/Solution

by : $329$

 * The Four Pennies
 * Take four pennies and arrange them on the table without the assistance of another coin or any means of measurement,
 * so that when a fifth penny is produced it may be placed in exact contact with each of the four (without moving them)
 * in the manner shown in the diagram.
 * The shaded circle represents the fifth penny.


 * Dudeney-Puzzles-and-Curious-Problems-329.png


 * How should you proceed?

Solution
Arrange the pennies as follows.


 * Dudeney-Puzzles-and-Curious-Problems-329-solution-1.png

Note they have been labeled from $1$ to $4$.

Move penny no. $1$ to touch $2$ and $4$:


 * Dudeney-Puzzles-and-Curious-Problems-329-solution-2.png

Move penny no. $4$ to touch $2$ and $3$:


 * Dudeney-Puzzles-and-Curious-Problems-329-solution-3.png