A real number is a value that represents a quantity along a continuous line. Real numbers can be positive or negative, and include such values as 1, 2, 3, 4, 5, -1, -2, -3, -4, -5, 0.5, 1.5, 2.5, and so on. Real numbers can also be represented using decimal notation, such as 3.14159 for pi.

#### What is not a real number?

There are a few different types of numbers that are not considered to be real numbers. These include imaginary numbers, complex numbers, and infinitesimal numbers.

Imaginary numbers are numbers that cannot be expressed as a real number. Examples of imaginary numbers include the square root of -1 and the cube root of -1.

Complex numbers are numbers that have both a real and imaginary component. For example, the number 3 + 4i is a complex number.

Infinitesimal numbers are numbers that are so small that they cannot be measured. These numbers are often used in calculus and other mathematical disciplines that deal with very small values.

### What are the 4 types of real numbers?

There are four types of real numbers: rational numbers, irrational numbers, whole numbers, and natural numbers.

Rational numbers are numbers that can be expressed as a fraction, where the numerator and denominator are both integers. Examples of rational numbers include 3/4, 2/5, and 1/2.

Irrational numbers are numbers that cannot be expressed as a fraction. Examples of irrational numbers include √2 and π.

Whole numbers are numbers that can be expressed as an integer. Examples of whole numbers include 0, 1, 2, 3, and 4.

Natural numbers are numbers that can be expressed as a positive integer. Examples of natural numbers include 1, 2, 3, 4, and 5. How many are real numbers? There are infinitely many real numbers. Is zero a real number? Zero is indeed a real number, and it is the smallest real number. Zero is also an even number. Is 3. 1415 a real number? Yes, 3.1415 is a real number. It is the value of pi, which is the ratio of the circumference of a circle to its diameter.