Red candle:
Initial height = 8 in
Burn rate = 710 in/h
After x hours, the height will be
h₁ = 8 - 710x
Blue candle:
Initial height = 6 in
Burn rate = 15 in/h
After x hours, the height will be
h₂ = 6 - 15x
When the two heights are equal, then
h₁ = h₂
8 - 710x = 6 - 15x
-695x = -2
x = 0.00288 hours
Answer:
The answer may take one of these forms:
0.003 hours, or
0.0029 hours, or
0.00288 hours.