Question 244516
If an eight inch candle is lighted at one end and placed in a horizontal position it will burn out in three hours. But after it burns for 1 1/2 hours, the other end is lighted and it burns at both ends. How long will the candle last?

This is a poorly worded problem.
I will also assume that the candles are otherwise equal in material and length.

From the first experiment we see that the candle burns at a rate of 8 inches in 3 hours.
So after 1 1/2 hours 4 inches have burned leaving 4 more inches.  if we now double the rate of burn by burning from both ends we get a rate of 8 inches in 1 1/2 hrs or 4 inches in 45 minutes.
so the candle will last the first 1 2/4 hours plus 45 minutes (3/4 )more after the second end is lit.
1 2/4 plus 3/4= 1 5 /4 or 2 1/4 hours total burn for the second candle