0

I only have two candles, each candle burns for exactly one hour. I do not know the length of the candle. Guessing and estimation is not allowed. You are not allowed any other materials other than the two candles (and a lighter I suppose).

EDIT:

I made a mistake, the candles burn for two hours, not one.

Oreo
  • 769
  • 6
  • 17
  • 1
    not an exact duplicate, the ratios are different. – Jasen May 08 '16 at 12:16
  • Agreed @Jasen ${}$ – warspyking May 08 '16 at 12:32
  • @Jasen The ratio is different, but the solution works the same way. The only difference is that you start counting time when the first candle/rope is finished. – f'' May 09 '16 at 07:06
  • @f'' doesn't work after the 2 hour edit. – Jasen May 09 '16 at 07:09
  • 1
    @Jasen It works perfectly fine after the 2 hour edit. – f'' May 09 '16 at 07:11
  • then light both ends of the remaining 1 hour candle,.. ok. – Jasen May 09 '16 at 08:27
  • Are we suggesting that a candle that has been designed specifically to burn for an exact amount of time in normal fashion (upright, with the flame and heat travelling up, directly opposite the rest of the candle) will burn exactly as fast as a candle which is lying horizontally (with the flame and heat travelling up, perpendicularly to the rest of the candle)? Methinks not. What if we had it at 45 degrees, with the wick on the down-facing end? or at 180 degrees, with the bulk of the candle directly above the flame? hmmm – Chowzen May 22 '16 at 12:08
  • I think this puzzle is different in the fact that you have to burn at one of its edges. – Xwtek Oct 02 '20 at 06:22

2 Answers2

1

Light one candle at both ends. When it is done burning, half an hour has passed.
Do what you want with the other candle. You don't need it.

Marius
  • 18,049
  • 4
  • 54
  • 101
  • well, ideal candles may burn equally fast at both ends, but real candles seem to burn at an accelrated rate due to wax dripping off. – Jasen May 08 '16 at 04:55
  • 2
    @Jasen: It doesn't matter whether it burns at the same speed. As long as the whole candle takes an hour, then the whole candle from both sides will take half an hour. – Deusovi May 08 '16 at 05:11
0

If you are in a hurry.

balance one candle across the other (lying down), where it is balanced is half its length cut or mark it there, then burn it to the mark.

if you have plenty of time to prepare

do the above to get two "half" candles , bur both of them and the whole candle, if one half burs out, divide the remainining half-candle,

When the split candle is entirely consumed the whole candle will be half burned, extinguish it and save it for when you need to time half an hour.

Jasen
  • 3,010
  • 13
  • 15
  • Sorry, Jasen. This approach requires that you estimate half and I explicitly said that the answer had to be exact and could not use estimation. Good try though. – Oreo May 08 '16 at 04:43
  • 1
    Thats first option is a measurement, not estimating. perhaps you should update your problem with a list of what actions are allowed. – Jasen May 08 '16 at 07:51