In a certain population, there are three times as many people aged 21 or under as there are people over The ratio of those 21 or under to the total population is:

let's say that there is 1 person over twenty-one. If there are 3 times as many people aged twenty-one or under as there are people over twenty-one, then there must be 3 people aged twenty-one or under. This means the TOTAL population = 1 + 3 = 4 The ratio of those twenty-one or under to the total population = 3 : 4