You have two ropes of equal length and a book of matches. If you were to light the end of one of the
ropes, it would burn for exactly one hour. By lighting the ropes in different ways, it is possible to
measure different lengths of time. One hour is one example of a length of time that can be measured. How
many different lengths of time in all can potentially be measured with the two ropes?
A couple of rules/restrictions:
1. You may not use scissors.
2. The rope is too rigid to be folded in half.
3. You can not tell by eye where the half way point of the string is.
ANSWER:
5.
EXPLANATION: The first four are relatively easy to find:
1) 30 minutes: by lighting one rope on each end.
2) 1 hour: by lighting one rope and then lighting the second when the first rope burns out.
3) 1.5 hours: by lighting one rope and then lighting each end of the second rope when the first burns out.
4) 2 hours: by lighting one rope and then lighting the second rope when the first rope burns out.
The fifth one is a little trickier:
5) 45 minutes: by lighting one rope on each end and lighting the second rope. When the first rope burns out,
light the other end of the second rope. :-)
Do you have a
suggestion for this puzzle (e.g. something that should
be mentioned/clarified in the question or solution, bug, typo, etc.)?
