IKMC 2024 - Grades 11-12 - Set 2 - Self-study Question 20

Question 20

Two candles of equal initial length are lit together. One burns completely in 4 hours, the other in 5 hours, at constant rates. After how many hours is one exactly three times as long as the other?

$40/11$
$45/12$
$63/20$
$3$
$47/14$