26 Jul
Unbraiding Braids
Three ropes have been fastened to a horizontal plunk, tangled a little as if one tried to make a braid and, lastly, loosely attached to an auxiliary plank to keep them braided.
Down below there is a third plank. The task is to attach three additional ropes to the first ones at one end and to the third plank at the other. Is it possible to perform that feat so that when the provisional plank is removed the ropes come undone?
Solution
Reflect the whole picture in the auxiliary plank. This will show how to attach the two sets of ropes. This is a fantastic exercise even for little kids.
This solution can be verified with real ropes, or with the shuttle puzzle.
References
- C. W. Trigg, Mathematical Quickies, Dover, 1985, #39.
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