This month's Puzzle Corner is a classic pencil and paper puzzle from the field of recreational mathematics that has challenged puzzle-solvers for many years. This is one of those puzzles that can be attempted for hours and hours without success, leading one to think that it truly is impossible. But, once a critical leap of insight is made, it can be solved in a matter of seconds. Because this puzzle can be quite frustrating, it is not a good one to give to students who haven't had much experience with puzzles. It requires persistence -- a key trait of experienced puzzlists. However, if your students have had a steady diet of puzzles and have developed some persistence, this puzzle will provide just the challenge they need.
The puzzle is a drawing of three houses across from three utilities -- the gas, water, and electric stations. The challenge is to connect each house with all three stations by drawing lines from the stations to the houses. The only restriction is that none of the utility lines that you draw may cross each other. (Hint: The wording of this last line is very important in making the leap of insight necessary to solve this puzzle.)
For this puzzle each student will need a copy of the student pages, a pencil and an eraser. Because it will likely take students many attempts to solve the puzzle, a second worksheet has been provided with four smaller versions. Even so, students may go through several copies of this second page before they discover a solution. Another option is to laminate a few of the student pages and set them at a center. This way students can use dry erase or overhead markers to work on the puzzle, thus saving some wear and tear on their erasers!
If you have not done this puzzle before, I strongly recommend that you try to solve it yourself before giving it to your students. This will help you understand the difficulties and frustrations they will encounter. If you are successful at solving the puzzle, it will enable you to give students some hints and/or guidance without giving away the solution.
I hope you and your students enjoy tackling this classic puzzle.