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Question 1
Write the additive inverse of each of the following:
- 1
- $\frac {-1}{9}$
- $ \frac {-2}{3}$
- 2
- $\frac {-9}{1}$
Solution
(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
- 0
- None of the above
Solution
Additive Identity is same for all Numbers and it is 0
Question 3
True or False Statement
- The difference of two rational number is a rational number
- Addition of rational numbers is associative
- Addition of rational numbers is commutative
- Subtraction of rational numbers is not commutative
- The addition or subtraction of two rational number is a rational number
Solution
All the statement are true
Question 4
Find the multiplicative inverse of the following.
- $ \frac {-11}{12}$
- $ \frac {-10}{9}$
- $ \frac {1}{2}$
- $\frac {-5}{2} \times \frac {-2}{5}$
- $\frac {-1}{2} \times \frac {-2}{5}$
- - 4
Solution
- $ \frac {-11}{12}$
Multiplicative inverse =>$ \frac {-12}{11}$
- $ \frac {-10}{9}$
Multiplicative inverse =$ \frac {-9}{10}$
- $ \frac {1}{2}$
Multiplicative inverse =2
- $\frac {-5}{2} \times \frac {-2}{5} =1$
Multiplicative inverse =1
- $\frac {-1}{2} \times \frac {-2}{5} = \frac {1}{5}$
Multiplicative inverse =5
- -4
Multiplicative inverse =-1/4
Question 5
Which of these properties hold false for Multiplication of rational numbers?
- Associative law
- Closure law
- Commutative law
- Existence of Multiplicative identity
- None of the these
Solution
None of these
Question 6
Find the below multiplication
- $ \frac {-1}{2} \times \frac {9}{10}$
- $ \frac {-25}{9} \times \frac {1}{3}$
- $\frac {7}{24} \times 10$
Solution
- $ \frac {-1}{2} \times \frac {9}{10}$
$=\frac { -1 \times 9}{2 \times 10} = \frac {-9}{20}$
- $ \frac {-25}{9} \times \frac {1}{3}$
$= \frac {-25 \times 1}{9 \times 3}= \frac {-25}{27}$
- $\frac {7}{24} \times 10$
$= \frac {7 \times 10}{24}= \frac {70}{24}$
Question 7
Find the following
- (1/2)-1
- (3)-1
- (-6)-1
- (1/-2)-1
Solution
- Multiplicative inverse of (1/2) =2
- Multiplicative inverse of (3) =1/3
- Multiplicative inverse of (-6) =-1/6
- 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?
Solution
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 __________.
Solution
- 4/5
- 1 and -1
- 1
- 3
- Rational Number
- Negative rational number
Question 12
Write five rational numbers which are smaller than 5
Solution
Answer:
0,1,2,3,4
Question 13
Find five rational numbers between (1) and 2
Solution
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
Question 14
A car travels a distance 50/3 km in 1/6 hours. What is the speed of the Car?
Solution
Speed = Distance/Time
$s=\frac {50/3}{1/6}= \frac {50}{3} \times \frac {6}{1}=100$ km/hr
Summary
This Rational numbers class 8 important questions is prepared keeping in mind the latest syllabus of CBSE . This has been designed in a way to improve the academic performance of the students. If you find mistakes , please do provide the feedback on the mail.
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