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.)
+36916 She has a total burn time of 3 + 4 + 5 = 12 hours
if two are burning at a time she has a total time available of 12 / 2 = 6 hours
