Question

the candles of equal length start burning at the same time. One of the candles takes 5 hours to burn completely whereas the other candle takes 4 hours to burn completely. After burning for certain time, the length of one candle is twice the length of other candle. Find the time the candles have already burned.

Answer 1

let the lenght be x 
x+2x = 5 +4
3x= 9
x= 3
2x=6