Test: Rational Numbers- 2 - Class 8 MCQ

In multiplicative inverse we reciprocal the numbers by which we get the answer =1 that's why 1/4×4/1 which we consider as 4 so 4 is the multiplicative inverse of 1/4

additive inverse means adding what number will give you zero 
so let that no be x 
x + 4/5 = 0
x = -4/5
trick : just change the sign of number

1 is the Multiplicative identity for rational numbers.

This is how associative property works. It states that you can add or multiply numbers regardless of how they are grouped. Addition and multiplication are associative for rational numbers. Subtraction and division are not associative for rational numbers.

1 because the reciprocal of 1 is 1/1 which is equal to 1.

Rational numbers are closed under subtraction.Because if we subtract a rational number with another rational number we will get rational number. For example 45−35 = 10, which is also a rational number.
Correct option is C.

Zero has no reciprocal. Because 1/0 is not defined and also remember any number multiplied by zero gives 0. Therefore, if reciprocal was supposed to be there then that reciprocal when multiplied by 0 should give 1 which is not possible.

Product of two rational numbers is always a rational number.
For example, 1/2 + 1/2 = 1

Given, A rational number is defined as a number that can be expressed in the form p/q , where p and q are integers

We have to find the condition that satisfies the definition.

A number that can be expressed in the form p/q , where p and q are integers and q ≠ 0, is called a rational number.

Therefore, the condition that satisfies the definition is q ≠ 0

(by using commutativity and associativity)

LCM of 7 and 21 is 21; LCM of 11 and 22 is 22)

Multiplicative inverse is nothing but a reciprocal of a number 2/9 which is 9/2.

A rational number between a and b is (a + b)/2
clearly it is there half so it will be between them
where a and b are numbers
a = 1/4, b = 1/2
Therefore, rational no. between 1/4 and 1/2 is
= (1/4 + 1/2)/2
=  [(1 + 2)/4]/2 
= 3/8

If you multiply any number with 1,the product will always be the same number which you multiply with 1. Therefore, 1 is the multiplicative identity.

Rational Numbers: This set is closed under addition, subtraction, multiplication, and division (with the exception of division by 0).