You have two ropes. You know that each rope takes one hour to burn from one end to the other, but that the burning does not take place at a constant rate (i.e. half the rope may burn in one minute, and the other half will take 59 more minutes to burn).
How would you go about measuring a 45 minute time interval with just these two ropes?
Start both ends of the first rope and one end of the second rope burning at the same time ( = time zero). The first rope will take a half hour to burn. At that point, when the first rope is completely burned, start the second end of the second rope on fire. It will take 15 more minutes to complete the burning of the second rope. At the time the second rope is completely burned, 45 minutes will have elapsed.
try this
