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Ncert Solutions for rational Numbers Class 8 CBSE Part 1


In this page we have NCERT book Solutions for Class 8th Maths:Rational Numbers for EXERCISE 1 . Hope you like them and do not forget to like , social share and comment at the end of the page.

Question 1:  

Using appropriate properties find:


Answer

  1. Using commutativity property of rational number

    Now using Distributivity property

     

    (ii) Using commutativity property of rational numbers

       Now using Distributivity property

Question 2    

Write the additive inverse of each of the following:

  1. 2/8
  2. -5/9
  3. -6/-5
  4.  2/-9
  5. 19/-6


Answer:

(i) 2/8

Additive inverse = -2/8

(ii) -5/9

Additive inverse = 5/9

(iii) -6/-5 =6/5

Additive inverse = -6/5

(iv)  2/-9=-2/9

Additive inverse =2/9

(v) 19/-6=  -19/6

Additive inverse =19/6

Question 3

Verify that - ( - x) = x for.

(i) x =11/15 (ii) x=-13/17

Answer:

  1.  x=11/15

    Additive inverse

        -x=-11/15  

    As   (11/15)   + (-11/15) =0

    The above   also represent that additive inverse of (-11/15) is (11/15) or we can say that

    - (-11/15)=11/15

    Or x=-(-x)

x=-13/17

Additive inverse

    -x=-13/17  

As   (-13/17)  + (13/17) =0

The above also represent that additive inverse of (13/17) is (-13/17)) or we can say that

- (13/17) = -13/17

Or x=-(-x)

 

Question 4

Find the multiplicative inverse of the following.

  1. -13
  2. -13/19
  3.  1/5
  4. -5/8 X -3/7
  5. -1 X -2/5
  6.  - 1


Answer

  1. -13

    Multiplicative inverse =-1/13

  2. -13/19

    Multiplicative inverse =-19/13

  3. 1/5

    Multiplicative inverse =5

  4. -5/8 X -3/7 =15/56

    Multiplicative inverse =56/15

  5. -1 X -2/5 =2/5

    Multiplicative inverse =5/2

-1

Multiplicative inverse =-1

 

Question 5  :

Name the property under multiplication used in each of the following:

Answer:

  1. 1 is the multiplicative identity
  2. Commutatively
  3. Multiplicative inverse

 

Question 6:  

Multiply 6/13 by the reciprocal of -7/16

Answer

Reciprocal of -7/16= -16/7

So (6/13) X (  -16/7) =-96/91

Question 7  

Tell what property allows you to compute

Answer:

Associativity

Question 8  

Is   8/9 the multiplicative inverse of 

Why or why not?

Answer:

=-9/8

Now

(8/9) X   (-9/8)   = -1

So it is not the multiplicative inverse

Question 9   

Is 0.3 the multiplicative inverse  of

 Why or why not?


Answer:

=10/3

Now

(3/10) X   (10/3)  =1

So it is the multiplicative inverse

Question 10    

Write:

(i) The rational number that does not have a reciprocal.

(ii) The rational numbers that are equal to their reciprocals.

(iii) The rational number that is equal to its negative.


Answer:

  1. 0
  2. 1 and -1
  3. 0

 

Question 11 :

Fill in the blanks.

(i) Zero has __________ reciprocal.

(ii) The numbers __________ and __________ are their own reciprocals

(iii) The reciprocal of - 5 is __________.

(iv) Reciprocal of (1/x)   where is x ≠ 0 __________.

(v) The product of two rational numbers is always a __________.

(vi) The reciprocal of a positive rational number is __________.


Answer:

  1. No
  2. 1 and -1
  3.  -1/5
  4. X
  5. Rational Number
  6. Positive rational number

     


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