Two candles have the same length,
but one will burn down in seven hours, the other in eleven.
If they are lighted at the same time,
when will one be twice as long as the other?
[SECRET]
Q: 양초를 영어로 쓰시오.
A:candle
[Solution]
The big candle burns t/11 of its height in t hours,
so the fraction remaining after that time is (1-t/11).
For the narrower candle the fraction remaining is (1-t/7).
The narrower one will be shorter, so the equation is (1-t/11)=2(1-t/7).
Solving gives t=77/15 hours, or 308 minutes.
[/SECRET]
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