1)
A number is considered a rational number if it can be written as one integer divided by another integer. Sometimes this is referred to as a simple fraction.
The number 1/2 is a rational number because it is written as the integer 1 divided by the integer 2. The number 5 is a rational number because we can write it as 5/1. We can also write it as 15/3 or 50/10 because 15 divided by 3 or 50 divided by 10 both equal 5. The mixed number 1 ½ is also a rational number because we can write it as 3/2.
2)
We can insert infinitely many rational numbers between any two rational numbers. This property of rational numbers is known as the dense property.