If there are twice as many apples as oranges, then there is 1 orange
for every 2 apples. So the barrel has 2/3 apples. Out of the
apples, there are 4 times as many are red as yellow. So for every
4 red, there is one yellow. That means that 1/5 of the apples are
yellow. If you are looking for yellow apples, the probability
of drawing one is
(2 / 3) * (1 / 5) =2/15