At 150 minutes the length of the first candle is 3 times that of the other.
The complete question is
There are two candles of same length and same size. Both of them burn at uniform rate. The first one burns in 5 hours and the second one burns in 2 hours. Both the candles are lit together. After how many minutes the length of the first candle is 3 times that of the other?
When two algebraic expression are equated using an equal sign an equation is formed.
First candle burns for 5 hours
Second candle burns for 2 hours
Let the length of candle be l.
After t time (in minutes), length of first candle =l−(lt/300)
Length of second candle =l− (lt/120)
From the data given
l - (lt/120) = 3 * (l−(lt/300))
On simplifying
4t = 600
t = 150 minutes
Therefore after 150 minutes the length of the first candle is 3 times that of the other.
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