Dora has three candles, which will burn for 3, 4 and 5 hours, respectively. If she wants to keep two candles burning at all times, what is the greatest number of hours she can burn the candles? (Dora has a clock that she can use to time the candles.) Please help me
Well, if you started to burn two candles at once. Which of the three would last longest? The five hour one of course.
So say you have the 5 hour candle and 4 hour candle burning. The 5 hour candle remains after four hours (one hour remains on the candle). You quickly replace the melted candle with the three hour candle, after one more hour (5 hours have passed) the only candle that remains is three hour (now one hour left).