Click here to purchase the entire book in PDF format. Rational Numbers Eventually, after you learned about counting and numbers, you were taught how to divide. When someone said ``20 divided by 5 equals 4'' then they meant ``if you have 20 sticks, then you could put those sticks in 4 piles with 5 sticks in each pile.'' Eventually, you learned that the division of one number by another can be written as a fraction like $\frac{3}{1}$ or $\frac{20}{5}$ or $\frac{5}{4}$ or $\frac{1}{3}$. If you do that division the old-fashioned way, you get numbers like this: $3/1 = 3.000000000$ etc... $20/5 = 4.00000000$ etc... $5/4 = 1.200000000$ etc... $1/3 = 0.333333333$ etc... The thing that I'm trying to point out here is that eventually, these numbers start repeating sometime after the decimal point. These numbers are called rational numbers.