This topic is in the 'Percents' section. It turns out that percents are just special kinds of ratios that always have 100 in the denominator. They are really useful, because they give you information relative to the same exact number, so it becomes easier to compare things. For example, if you're hungry, would you rather have 41.7% of a pizza or 42.9% of a pizza? Well, 42.9 is bigger than 41.7, so that's an easy question:) But it would have been harder if you had to decide between 3/7 of a pizza and 5/12 of a pizza, because the denominators are different and it's hard to visualize the differences between 1/7 and 1/12. If you convert the fractions, it turns out that 3/7 is 42.9% and 5/12 is 41.7% so you can see some of the advantages that percents give us right away! There are many more applications to learn about, so check out the tutorials that this section has to offer.