Last updated on July 15th, 2025
In rational numbers, zero is known as the additive identity because adding 0 to any number does not change its value. Another important property is the additive inverse. The additive inverse of a number is what you add to it to get zero. Therefore, the additive inverse of any rational number a/b is -a/b.
Rational numbers are numbers in the form of p/q, where p and q can be any integer and q ≠ 0. Natural numbers, whole numbers, integers, fractions, and decimals (terminating and recurring decimals) are all considered rational numbers.
‘Rational’ is derived from ‘ratio’. Therefore, the idea of fractions, which represent ratios, is closely tied to rational numbers. In simple words, a number is called rational if it can be written as a fraction where both the numerator and the denominator are integers (the denominator is not zero).
The additive identity property states that adding 0 to a number does not change its value: a + 0 = a. For example, take the rational number ⅖, and its additive inverse is -⅖. According to the property:
2/5 + (-2/5) = 0
Thus, the property is verified.
Two real numbers are said to be additive inverses of each other if their sum equals zero. In general, for any real number R, we have:
R + (-R) = 0
Here, R and -R are additive inverses of each other. Since rational numbers belong to the set of real numbers, this rule applies to them as well.
For example, if you take the rational number ⅚, its additive inverse is -⅚.
So: 5/6 + (-5/6) = 0.
Here, 5/6 is the additive inverse of -5/6, and vice versa.
The additive identity property states that when you add zero to any number, the value of the number stays the same.
In a mathematical system, the additive identity is an element that, when added to a number, does not change its value. For the set of rational numbers, this identity is 0. The additive identity property states that adding 0 to any number results in the same number:
a + 0 = 0 + a
For the additive inverse, a number and its inverse must sum to zero. For example, the additive inverse of -5/7 is 5/7, since:
(-5/7) + (5/7) = 0
For the multiplicative inverse, multiplying a number by its reciprocal results in 1. For example, the multiplicative inverse of 4/9 is 9/4, since:
(4/9) × (9/4) = 1
The additive identity of rational numbers (0) has practical applications in various real-life situations. Here are a few examples:
While this concept seems simple, students often make common mistakes when applying it. Below are some frequent errors and tips to avoid them.
What is the sum of 5/7 and 0?
5/7 + 0 = 5/7
According to the additive identity property, adding 0 to any rational number does not change its value.
Find the result of (-¾) + 0.
(-3/4) + 0 = -¾
Since 0 is the additive identity, adding it to -¾ keeps the number unchanged.
Find the result of 0 + 9/11?
0 + 9/11 = 9/11
The order of addition does not matter; adding 0 before or after a number keeps it the same.
If x + 0 = 2/5, what is the value of x?
2/5
Since adding 0 does not change the number, x must be 2/5.
A fruit seller has 12.5 kg of apples. If no apples are added to the stock, how much does the stock of apples weigh now?
12.5 kg + 0 kg = 12.5 kg
Adding zero means no change in quantity, so the total remains 12.5 kg.
Hiralee Lalitkumar Makwana has almost two years of teaching experience. She is a number ninja as she loves numbers. Her interest in numbers can be seen in the way she cracks math puzzles and hidden patterns.
: She loves to read number jokes and games.