Real Numbers
Real numbers are the numbers we use in everyday life. Whether you're counting your books, measuring the length of a table, or calculating the price of groceries, you're probably using real numbers. Understanding real numbers is fundamental in mathematics and is useful in a variety of practical applications.
What are real numbers?
Real numbers include all the numbers present on the number line. It includes different categories of numbers such as natural numbers, whole numbers, integers, rational numbers, and irrational numbers. These categories together form the group of real numbers.
Real Numbers = Natural Numbers ∪ Whole Numbers ∪ Integers ∪ Rational Numbers ∪ Irrational Numbers
Natural numbers
Natural numbers are the numbers we use for counting. These are the numbers starting at 1 and continuing to infinity: 1, 2, 3, 4, etc. They do not include 0 or any fractions or decimals.
Whole numbers
Whole numbers are like natural numbers, but they include 0. So, whole numbers are 0, 1, 2, 3, 4, etc. Again, they do not include fractions or decimals.
Integers
Integers extend whole numbers to include negative numbers. Thus, integers are ...-3, -2, -1, 0, 1, 2, 3, etc. Integers are considered as the sum of whole numbers and their opposites. Think in terms of form.
Rational numbers
Rational numbers are numbers that can be expressed as the quotient or fraction of two integers. A rational number is written in the form a/b
, where a
and b
are integers, and b
is not zero. For example:
3/4
(three-fourth)-5/6
(negative five-sixth)2
(which can be written as2/1
)-10
(which can be written as-10/1
)
All integers are rational numbers because their denominator can be 1.
Irrational numbers
Irrational numbers are numbers that cannot be written as simple fractions. They have endless non-repeating decimal parts. Examples include:
- The square root of 2 (
√2
), which is approximately 1.414213... - The number
π
(pi), which is approximately 3.141592...
Irrational numbers fill in the "gaps" on the number line that rational numbers do not fill.
Properties of real numbers
Real numbers obey several fundamental properties that help us perform arithmetic operations and solve mathematical problems. These properties include:
Commutative property
This property states that changing the order of numbers in an addition or multiplication operation does not change the result. For example:
a + b = b + a
a × b = b × a
Example: 3 + 5 = 5 + 3 = 8
or 4 × 7 = 7 × 4 = 28
.
Associative property
This property states that when three or more numbers are added or multiplied, the grouping of the numbers does not affect the sum or product. For example:
(a + b) + c = a + (b + c)
(a × b) × c = a × (b × c)
Example: (2 + 3) + 4 = 2 + (3 + 4) = 9
or (5 × 6) × 2 = 5 × (6 × 2) = 60
.
Distributive property
This property states that multiplying a number by a sum is the same as doing each multiplication separately. For example:
a × (b + c) = (a × b) + (a × c)
Example: 3 × (4 + 5) = 3 × 4 + 3 × 5 = 12 + 15 = 27
.
Identity property
The identity property of addition states that the sum of any number and zero is itself a number, and the identity property of multiplication states that the product of any number and one is itself a number. For example:
a + 0 = a
a × 1 = a
Example: 7 + 0 = 7
or 9 × 1 = 9
.
Conclusion
Real numbers are an essential part of mathematics and are highly applicable in real-life situations. They include a wide range of numbers from whole numbers to fractions, as well as non-terminating and non-repeating decimals (irrational numbers). Understanding the properties of real numbers will help you perform arithmetic operations easily and solve various mathematical problems.
Summary example
Let's summarize this with some examples using real numbers:
- If you add 2.5 (a rational number) and
√2
(an irrational number), you still get a real number. - An integer such as -7 can be easily added to another integer such as 10 to get 3, which is also a real number.