A rational number is a number that can be made by dividing two integers. An integer is a number that doesn't have a fraction part.
1. 2.4 - rational 2. 74 - rational 3. 17.3333333… - rational 4. π -irrational 5. there is no number 6. –18 - rational 7. there is no number 8. 87.125 - rational 9. –30 - rational 10. –8.3 -rational 11. 58.25 -rational 12. 121 -rational 13. 4.5 -rational 14. 3 7/10 -rational
As you can see, most numbers are rational. But, when you come across pi or when you have a decimal that goes on forever without repeating (like some square roots), it tends to be irrational.