Puzzle #198: Can you measure your turkey’s roasting time?

#198 Christmas candles

set by Paulo Ferro

Your turkey needs exactly 6 hours to slow roast. Alas, you have no timer, just three candles: one that burns in 3 hours, one that burns in 4 hours and another that burns in 5 hours.

How can you measure 6 hours using these candles, putting the roast in the oven at the same time as you light the first candle?

#198 Christmas candles

Solution

Here is one way. Light all three candles. When the 3-hour candle burns out, blow out the 4-hour candle. When the 5-hour candle burns out, relight the 4-hour…