SOLUTION: One candle will burn up completely in 4 hours, while a second candle of equal length requires 5 hours to burn up completely. If the candles are lit at the same time, how long will

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Question 408976: One candle will burn up completely in 4 hours, while a second candle of equal length requires 5 hours to burn up completely. If the candles are lit at the same time, how long will they burn before one is exactly three times as long as the other?
Found 2 solutions by scott8148, ankor@dixie-net.com:
Answer by scott8148(6628) About Me  (Show Source):
You can put this solution on YOUR website!
3[1 - (x / 4)] = 1 - (x / 5)

3 - (3x / 4) = 1 - (x / 5)

multiplying by 20 (LCD) ___ 60 - 15x = 20 - 4x

40 = 11x ___ 40/11 = x

Answer by ankor@dixie-net.com(22740) About Me  (Show Source):
You can put this solution on YOUR website!
One candle will burn up completely in 4 hours, while a second candle of equal
length requires 5 hours to burn up completely.
If the candles are lit at the same time, how long will they burn before one is
exactly three times as long as the other?
:
Assign a value to the length of the candles, 20"
then
20%2F4 = 5 in/hr burn rate of candle 1
and
20%2F5 = 4 in/hr burn rate of candle 2
:
let t = time for candle 2 to be 3 times candle 1
:
Candle 2 = 3 times candle 1
(20 - 4t) = 3(20 - 5t)
20 - 4t = 60 - 15t
-4t + 15t = 60 - 20
11t = 40
t = 40%2F11
t = 37%2F11 hrs; 3 + 7%2F11*60 = 38.2 min
:
3 hrs 38.2 min, Candle 2 will be three times the length of candle 1