Selina Concise Mathematics Class 8 ICSE Solutions Chapter 1 Rational Numbers

Selina Concise Mathematics Class 8 ICSE Solutions Chapter 1 Rational Numbers

Selina Publishers Concise Mathematics Class 8 ICSE Solutions Chapter 1 Rational Numbers

Rational Numbers Exercise 1A – Selina Concise Mathematics Class 8 ICSE Solutions

Question 1.

Add, each pair of rational numbers, given below, and show that their addition (sum) is also a rational number:

  

Solution:
 
 
 
 
 
 
Question 2.
Evaluate:
 
Solution:
 
 
 
 
 
 
Question 3.
Evaluate:
 
Solution:
 
 
 
 
 
Question 4.

For each pair of rational numbers, verify commutative property of addition of rational numbers:

  

Solution:
 
This verifies the commutative property for the addition of rational numbers.
 
 
This verifies the commutative property for the addition of rational numbers.
 
 
This verifies the commutative property for the addition of rational numbers.
 
This verifies the commutative property for the addition of rational numbers.
 
This verifies the commutative property for the addition of rational numbers.
 
 
This verifies the commutative property for the addition of rational numbers.

Question 5.

For each set of rational numbers, given below, verify the associative property of addition of rational numbers:

  

Solution:
 
 
This verifies associative property of the addition of rational numbers.
 
 
This verifies associative property of the addition of rational numbers.
 
 
 
This verifies associative property of the addition of rational numbers.
 
 
Question 6.
Write the additive inverse (negative) of:
 
Solution:
 
Question 7.
Fill in the blanks:
 
Solution:
 
 
Question 8.
State, true or false:
 
Solution:
(i) False
(ii) False
(iii) True
(iv) True
(v) False
(vi) False

Rational Numbers Exercise 1B – Selina Concise Mathematics Class 8 ICSE Solutions

Question 1.
Evaluate:
 
Solution:
 
 
 
 
Question 2.
Subtract:
 
Solution:
 
 
 
 
Question 3.
The sum of two rational numbers is   . If one of them is   , find the other.
Solution:
The sum of two rational numbers = 
And, one of the numbers = 
The other rational number
 
Question 4.
The sum of the two rational numbers is   . If one of them is   , find the other.
Solution:
 
 
Question 5.
The sum of the two rational numbers is -6. If one of them is   , find the other.
Solution:
 
Question 6.
Which rational number should be added to   to get   ?
Solution:
 
Question 7.
Which rational number should be added to   to get   ?
Solution:
 
Question 8.
Which rational number should be subtracted from   to get   ?
Solution:
 
Question 9.
(i) What should be subtracted from -2 to get 
(ii) What should be added to -2 to get 
Solution:
 
 
Question 10.
Evaluate:
 
 
Solution:
 
 
 

Rational Numbers Exercise 1C – Selina Concise Mathematics Class 8 ICSE Solutions

Question 1.
Evaluate:
 
Solution:
 
 
Question 2.
Multiply:
 
Solution:
 
 
Question 3.
Evaluate:
 
Solution:
 
 
 
 
Question 4.
Multiply each rational number, given below, by one (1):
 
Solution:
 
 
Question 5.

For each pair of rational numbers, given below, verify that the multiplication is commutative:

  

Solution:
 
 
Question 6.

Write the reciprocal (multiplicative inverse) of each rational number, given below :

  

Solution:
 
Question 7.
Find the reciprocal (multiplicative inverse) of:
 
 
Solution:
 
Question 8.
 
Solution:
 
 
Question 9.
 
Solution:
 
 
Question 10.

Name the multiplication property of rational numbers shown below :

  

Solution:
(i) Commutativity property.
(ii) Associativity property.
(iii) Distributivity property.
(iv) Existence of inverse.
(v) Existence of identity.
(vi) Existence of inverse.

Question 11.
Fill in the blanks:
(i) The product of two positive rational numbers is always ……………
(ii) The product of two negative rational numbers is always ……………
(iii) If two rational numbers have opposite signs then their product is always …………..

(iv) The reciprocal of a positive rational number is ………. and the reciprocal of a negative raitonal number is ……………

(v) Rational number 0 has ………….. reciprocal.

(vi) The product of a rational number and its reciprocal is ………..
(vii) The numbers ……….. and ……….. are their own reciprocals.
(viii) If m is reciprocal of n, then the reciprocal of n is ………….
Solution:
(i) The product of two positive rational numbers is always positive.
(ii) The product of two negative rational numbers is always positive.
(iii) If two rational numbers have opposite signs then their product is always negative.

(iv) The reciprocal of a positive rational number is positive and the reciprocal of a negative raitonal number is negative.

(v) Rational number 0 has no reciprocal.

(vi) The product of a rational number and its reciprocal is 1.
(vii) The numbers 1 and -1 are their own reciprocals.
(viii)If m is reciprocal of n, then the reciprocal of n is m.

Rational Numbers Exercise 1D – Selina Concise Mathematics Class 8 ICSE Solutions

Question 1.
Evaluate:
 
 
Solution:
 
 
 
 
Question 2.
Divide:
 
Solution:
 
 
Question 3.
The product of two rational numbers is -2. If one of them is   , find the other.
Solution:
 
Question 4.
The product of two numbers is   . If one of them is   , find the other.
Solution:
 
Question 5.
m and n are two rational numbers such that
 
Solution:
 
Question 6.
By what number must   be multiplied so that the product is   ?
Solution:
 
Question 7.
By what number should   be multiplied to get 16?
Solution:
 
Question 8.
If 3   litres of milk costs ₹49, find the cost of one litre of milk?
Solution:
 
Question 9.
Cost of 3   metre of cloth is ₹88  . What is the cost of 1 metre of cloth?
Solution:
 
Question 10.
Divide the sum of   and   by   .
Solution:
 
 
Question 11.
 
Solution:
 
 
 
Question 12.

The product of two rational numbers is -5. If one of these numbers is   , find the other.

Solution:

 
 
Question 13.
 
Solution:
 
 

Rational Numbers Exercise 1E – Selina Concise Mathematics Class 8 ICSE Solutions

Question 1.
 
Solution:
 
Question 2.
 
Solution:
 
Question 3.
Insert one rational number between (0 7 and 8 (ii) 3.5 and 5
(i) 2 and 3.2
(ii) 3.5 and 5
(iii) 2 and 3.2
(iv) 4.2 and 3.6
(v)   and 2
Solution:
 
 
Question 4.
Insert two rational numbers between
(i) 6 and 7
(ii) 4.8 and 6
(iii) 2.7 and 6.3
Solution:
 
 
 
Question 5.
Insert three rational numbers between
(i) 3 and 4
(ii) 10 and 12
Solution:
 
Question 6.
Insert five rational numbers between   and 
Solution:
LCM of denominators 5 and 3 is 15
 
Question 7.
Insert six rational numbers between   and 
Solution:
 
 
Question 8.
Insert seven rational numbers between 2 and 3.
Solution: