How long after lighting, in hours, will the first candle be half the height of the second candle?

Question

Two candles of equal heights but different thicknesses are lit. The first burns off in 8 hours and the second in 10 hours. How long after lighting, in hours, will the first candle be half the height of the second candle? The candles are lit simultaneously and each burns at a constant linear rate.

Answer 1

I don't think that there's a definitive answer to this without at least one measurement. Firstly we don't know about other interfering variables like the brands of the 2 candles, the types, the ingredients, and loads more. It's impossible to provide an entirely correct answer without all of these things being clearly specified. However, one possible answer I did come up with was 6 hours.