Henry Ernest Dudeney/Puzzles and Curious Problems/228 - The Ladder

by : $228$

 * The Ladder
 * A ladder was fastened on end against a high wall of a building.
 * It was unfastened and pulled out $4$ yards at the bottom.
 * It was then found that the ladder had descended just one-fifth of the length of the ladder.
 * What was the length of the ladder?