NCERT Exemplar Class 8 Maths Unit 1 Rational Numbers

Candidates can download NCERT Exemplar Class 8 Maths Unit 1 from this page. The exemplar has been provided by the National Council of Educational Research & Training (NCERT) and the candidates can check it from below for free of cost. It contains objective, very short answer type, short answer type, and long answer type questions. Along with it, the answer for each question has also been provided. From the NCERT Exemplar Class 8 Maths Unit 1, candidates can understand the level and type of questions that are asked in the exam.

NCERT Exemplar Class 8 Maths Unit 1 Rational Numbers

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NCERT Class 8 Maths Unit 1 is for Rational Numbers. The type of questions that will be asked from NCERT Class 8 Maths Unit 1 are displayed in the below provided NCERT Exemplar Class 8 Maths Unit 1. With the help of it, candidates can prepare well for the examination.

Main Concepts and Results

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A number that can be expressed in the form p/q , where p and q are integers and q¹0, is called a rational number.
Lowest form of a rational number – A rational number p/ q is said to be in the lowest form or simplest form if p and q have no common factor other than 1 and q ¹ 0.

Addition, subtraction, multiplication and division of rational numbers are done in the same way as we do for fractions.
Rational numbers are closed under the operations of addition, subtraction and multiplication.
The operations of addition and multiplication for rational numbers are
(i) commutative (ii) associative

The rational number 0 is the additive identity for rational numbers and the rational number 1 is the multiplicative identity for rational numbers.
The additive inverse of the rational number a /b is –a /b and vice-versa.
The reciprocal or multiplicative inverse of the rational number a b is

Distributivity of rational numbers – For all rational numbers a, b and c.

Rational numbers can be represented on a number line.
Between any two given rational numbers there are infinitely many rational numbers. The idea of mean helps us to find rational numbers between two given rational numbers.

Solved Examples

Example 1: Which of the following is not true?

Solution: The correct answer is (b).

Example 2: Multiplicative inverse of 0/1 is

(a) 1 (b) –1 (c) 0 (d) not defined

Solution: The correct answer is (d).

Example 3: Three rational numbers lying between −3/4 and 1/2 are

Solution: The correct answer is (c).

Fill in the Blanks Solved Examples

Example 4: The product of a non-zero rational number and its reciprocal is ________.

Solution : 1

Example 5: If x = 1 /3 and 6 7 y = 6 /7then xy −y/x = _______.

Solution : −16/7

Statements are true or false

Example 10 : Let O, P and Z represent the numbers 0, 3 and -5 respectively on the number line. Points Q, R and S are between O and P such that OQ = QR = RS = SP. What are the rational numbers represented by the points Q, R and S. Next choose a point T between Z and O so that ZT = TO? Which rational number does T represent?

Think and Discuss

Explain the first step in solving an addition equation with fractions having like denominators.
Explain the first step in solving an addition equation with fractions having unlike denominators.

Observation

From (i) to (iii), we observe that: (i) When we add 0 to a rational number we get the same rational number. From (iv) to (vi), we observe that: (ii) When we multiply a rational number by 1 we get the same rational number. (iii) Therefore, 0 is the additive identity of rational numbers and 1 is the ‘multiplicative identity’ of rational numbers