Answer: After 4 hours both candles be at the same height .
Explanation:
Since we have given that
Height of red candle = 8 inches
Rate at which red candle is burning is given by
[tex]\frac{7}{10}\ inch\ per\ hour[/tex]
Height of blue candle = 6 inches
Rate at which blue candle is burning is given by
[tex]\frac{1}{5}\ inch\ per\ hour[/tex]
Let 'y' be the height of both the candles after burning
Let 'x' be the amount of time it burns in hours.
So, equation for red candle be
[tex]y=8-\frac{7}{10}x[/tex]
equation for blue candle be
[tex]y=6-\frac{1}{5}x[/tex]
According to question, we get
[tex]8-\frac{7}{10}x=6-\frac{1}{5}x\\\\8-6=\frac{7}{10}x-\frac{1}{5}x\\\\2=\frac{7x-2x}{10}\\\\2=\frac{5x}{10}\\\\2=\frac{1x}{2}\\\\2\times 2=x\\\\4\ hours=x[/tex]
Hence, after 4 hours both candles be at the same height .