> The bus driver’s watch was broken, and he needed to time 15 minutes. Luckily I had with me two ropes of varying density, both of which burn for exactly one hour…
Light both ends of one rope and one end of another. When the first rope is burnt, the time starts, light the other end of the second rope--it should burn for 15 minutes.
Light both ends of one rope and one end of another. When the first rope is burnt, the time starts, light the other end of the second rope--it should burn for 15 minutes.