Chapter 1: Number Systems

Rational Numbers

Definition

A rational number is any number that can be written as pq\frac{p}{q} where:

  • pp and qq are integers
  • q0q \neq 0

Understanding the Definition

What does "p/q form" mean?

It means we can express the number as a fraction of two integers.

Examples of Rational Numbers:

Numberp/q FormWhy it works
55/1Any integer can be written with denominator 1
-3-3/1Negative integers work too
0.51/2Terminating decimals are rational
0.333...1/3Repeating decimals are rational
00/1Zero is rational!

How Many Rationals Between Two Numbers?

Key Fact: There are infinitely many rational numbers between any two rational numbers!

Method to Find Rationals Between a and b:

Method 1: Average Method

  1. Find average: (a+b)/2(a + b) / 2
  2. This gives one rational between a and b
  3. Repeat to find more!

Method 2: Common Denominator Method

  1. Write both numbers with same denominator
  2. The numerators between them give you rationals
Visualizer
Number Line
0
1/2
1
3/2
2
natural
whole
integer
rational
irrational

Interactive Visualization