How to know what number is a rational number?

A rational number has an end but irrational doesn't (think of pi or 1/3); )

A rational number is a number that can be made by dividing two integers (an integer is a number with no fractional part). The word rational includes the word "ratio." Rational numbers are basically numbers, either positive or negative that you get by dividing 2 numbers. Any number is a rational number, even fractions and decimals, except pi due to the fact that it's a irrational number.

Step-by-step explanation:

Examples of rational numbers include, 1, which you get by dividing 1 by 1, 2 which you get by dividing 2 by 1 and 2.12, which you get by dividing 212 by 100.