18/90 = 20%
A value of 20% can show up in everyday life as a store discount, a tip, or the share of students who choose a particular activity. For example, if one out of five shoppers uses a coupon, that’s about the same share.
To picture it quickly, imagine a group of five equal parts and shade one part. You can also think of it as roughly two out of every ten things.
A common mistake is treating 20% as always meaning 20 items. It means one-fifth of the total, so the number of items depends on how large the whole group is.
