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Important questions for rational Numbers Class 8 CBSE





In this page we have Important questions for rational Numbers Class 8 CBSE . Hope you like them and do not forget to like , social share and comment at the end of the page.
Question 1
Write the additive inverse of each of the following:
  1. 1
  2. $\frac {-1}{9}$
  3. $ \frac {-2}{3}$
  4. 2
  5. $\frac {-9}{1}$
Answer
(i) 1
Additive inverse = -1
(ii) $\frac {-1}{9}$
Additive inverse = $\frac {1}{9}$
(iii) $ \frac {-2}{3}$
Additive inverse = $\frac {2}{3}$
(iv)  2
Additive inverse =-2
(v) -9/1=-9
Additive inverse =9
Question 2
What is the additive identity?
  1. 1
  2. -1
  3. 0
  4. None of the above
Answer   0
Question 3 
True or False Statement
  1. The difference of two rational number is a rational number
  2. Addition of rational numbers is associative
  3. Addition of rational numbers is commutative
  4. Subtraction of rational numbers is not commutative
  5. The addition or subtraction of two rational number is a rational number
Answer
All the statement are true
Question 4  
Find the multiplicative inverse of the following.
  1. $ \frac {-11}{12}$
  2. $ \frac {-10}{9}$
  3. $ \frac {1}{2}$
  4. $\frac {-5}{2} \times \frac {-2}{5}$
  5. $\frac {-1}{2} \times \frac {-2}{5}$
  6. - 4

Answer
  1. $ \frac {-11}{12}$
    Multiplicative inverse =>$ \frac {-12}{11}$
  2. $ \frac {-10}{9}$
    Multiplicative inverse =$ \frac {-9}{10}$
  3. $ \frac {1}{2}$
    Multiplicative inverse =2
  4. $\frac {-5}{2} \times \frac {-2}{5} =1$
    Multiplicative inverse =1
  5. $\frac {-1}{2} \times \frac {-2}{5} = \frac {1}{5}$
    Multiplicative inverse =5
  6. -4
    Multiplicative inverse =-1/4


Question 5
Which of these properties hold false for Multiplication of rational numbers?
  1.  Associative law
  2. Closure law
  3. Commutative law
  4. Existence of Multiplicative identity
  5. None of the these
Answer
None of these
Question 6
Find the below multiplication
  1. $ \frac {-1}{2} \times \frac {9}{10}$
  2. $ \frac {-25}{9} \times \frac {1}{3}$
  3. $\frac {7}{24} \times 10$
Answer
  1. $ \frac {-1}{2} \times \frac {9}{10}$
    $=\frac { -1 \times 9}{2 \times 10} = \frac {-9}{20}$
  2. $ \frac {-25}{9} \times \frac {1}{3}$
    $= \frac {-25 \times 1}{9 \times 3}= \frac {-25}{27}$
  3. $\frac {7}{24} \times 10$
    $= \frac {7 \times 10}{24}= \frac {70}{24}$
Question 7
Find the following
  1.  (1/2)-1
  2. (3)-1
  3. (-6)-1
  4. (1/-2)-1
Answer
  1. Multiplicative inverse of (1/2)   =2
  2. Multiplicative inverse of (3)   =1/3
  3. Multiplicative inverse of (-6)   =-1/6
  4. Multiplicative inverse of (1/-2)   =-2
Question 8  
The product of two rational number is 2   , if one of the rational number is 1/7  ,what is the value of other?
Answer:
Let a   be the other number, then
$a \times \frac {1}{7} =2$
Or
$a= 2 \div \frac {1}{7}$
$a=2 \times 7=14$
Question 11
Fill in the blanks
(i)  ____   ÷  (-3)=  (-4/15)
(ii) The numbers __________ and __________ are their own reciprocals
(iii) The reciprocal of   1   is __________.
(iv)   (1/2)   ÷  (2/3)  =__________.
(v) The product of two rational numbers is always a __________.
(vi)  The reciprocal of a negative rational number is __________.

Answer:
  1. 4/5
  2. 1 and -1
  3.  1
  4. 3
  5. Rational Number
  6. Negative rational number
Question 12
Write five rational numbers which are smaller than 5

Answer:
  0,1,2,3,4
Question 13
Find five rational numbers between (1) and 2
Answer:
We can write as
$1= \frac {10}{10}$
$2= \frac {20}{10}$
So five rational numbers will be
11/10, 12/10, 13/10,14/10,15/10

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Class 8 Maths Class 8 Science
Reference Books for class 8 Math

Given below are the links of some of the reference books for class 8 Math.

  1. Mathematics Foundation Course for JEE/Olympiad : Class 8 This book can take students maths skills further. Only buy if child is interested in Olympiad/JEE foundation courses.
  2. Mathematics for Class 8 by R S Aggarwal Detailed Mathematics book to clear basics and concepts. I would say it is a must have book for class 8 student.
  3. Pearson Foundation Series (IIT -JEE / NEET) Physics, Chemistry, Maths & Biology for Class 8 (Main Books) | PCMB Combo : These set of books could help your child if he aims to get extra knowledge of science and maths. These would be helpful if child wants to prepare for competitive exams like JEE/NEET. Only buy if you can provide help to the child while studying.
  4. Reasoning Olympiad Workbook - Class 8 :- Reasoning helps sharpen the mind of child. I would recommend students practicing reasoning even though they are not appearing for Olympiad.

You can use above books for extra knowledge and practicing different questions.







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