Word of caution here, as it depends a little on context.
Say you have a bag full of Blue and Red balls. I tell you that the ratio of blue balls to red balls is 1:5, and that there are 60 balls in total.
Now, this means that there are 1/5 as many blue balls as there are red balls. But it also means that the blue balls are 1/6 of the whole bag (1 in 6 of all the balls are blue).
Specifically, we know there are 10 blue balls and 50 red balls. 10/50 is 1/5. But 10/(10+50) is 1/6.
Does that help?