# Real Numbers

Real numbers are rational numbers plus irrational numbers.

Since rational numbers include integers and fractions, then real numbers include:

• integers {..., -5,-4,-3,-2,-1,0,1,2,3,4,5,...}
• fractions (proper, improper, mixed numbers)
• irrational numbers (like sqrt(2), root(3)(-15), pi, e etc.)

Set of real numbers, i.e. group of real numbers, is denoted by RR.

As we already saw, all these numbers can be placed on a number line, which is called real number line.

Real numbers are called "real", because they are used in math to represent something:

• pi is used to describe the ratio of circumference of any circle and its diameter
• sqrt(2) is used to describe diagonal of unit square
• 5/7 is used to describe 5 pieces of cake, that is divided into 7 pieces.