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?
:
Assign a value to the length of the candles, 20"
then
{{{20/4}}} = 5 in/hr burn rate of candle 1
and
{{{20/5}}} = 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 = {{{40/11}}}
t = 3{{{7/11}}} hrs; 3 + {{{7/11}}}*60 = 38.2 min
:
3 hrs 38.2 min, Candle 2 will be three times the length of candle 1