Use adaptive quiz-based learning to study this topic faster and more effectively.

# Real numbers

There are numbers that are not rational. These are called irrational numbers.

$\sqrt{2}$, the number whose square is $2$, is an irrational number.

Another irrational number is $\pi$, which is the area of a circle with radius $1$.

The collection of numbers that combines all the rational and irrational numbers is called the real numbers. The set of the real numbers is written as $\mathbb{R}$.

The set of the real numbers contains the rational numbers, the integers and the positive integers.