Exercise 1D
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Q1 | Ex-1D | Rational Numbers | Class 8 | RS AGGARWAL | Chapter 1 | myhelper
Question 1:
Find each of the following products:
(i)
(ii)
(iii)
(iv)
(v)
(vi)
(vii)
(viii)
(ix)
(x)
(xi)
(xii)
Answer 1:
(i)
(ii)
(iii)
Simplifying the above rational number, we get:
(iv)
Simplifying the above rational number, we get:
(v)
Simplifying the above rational number, we get:
(vi)
Simplifying the above rational number, we get:
(vii)
Simplifying the above rational number, we get:
(viii)
Simplifying the above rational number, we get:
(ix)
Simplifying the above rational number, we get:
(x)
Simplifying the above rational number, we get:
(xi)
Simplifying the above rational number, we get:
(xii)
Simplifying the above rational number, we get:
Q2 | Ex-1D | Rational Numbers | Class 8 | RS AGGARWAL | Chapter 1 | myhelper
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Question 2:
Verify each of the following:
(i)
(ii)
(iii)
(iv)
Answer 2:
(i)
LHS = RHS
(ii)
$\frac{-8}{7} \times \frac{13}{9}=\frac{13}{9} \times \frac{-8}{7}$
LHS$=\frac{-8}{7} \times \frac{13}{9}=\frac{(-8) \times 13}{7 \times 9}=-\frac{104}{63}$
RHS$=\frac{13}{9} \times \frac{-8}{7}=\frac{13 \times(-8)}{9 \times 7}=-\frac{104}{63}$
LHS=RHS
(iii)
LHS = RHS
(iv)
LHS = RHS
Q3 | Ex-1D | Rational Numbers | Class 8 | RS AGGARWAL | Chapter 1 | myhelper
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Question 3:
Verify each of the following:
(i)
(ii)
(iii)
Answer 3:
(i)
∴
(ii)
∴
(iii)
∴
Q4 | Ex-1D | Rational Numbers | Class 8 | RS AGGARWAL | Chapter 1 | myhelper
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Question 4:
Fill in the blanks:
(i) $\frac{-23}{17} \times \frac{18}{35}=\frac{18}{35} \times(\ldots \ldots)$
(ii) $-38 \times \frac{-7}{19}=\frac{-7}{19} \times(\ldots \ldots)$
(iii) $\left(\frac{15}{7} \times \frac{-21}{10}\right) \times \frac{-5}{6}=(\ldots \ldots) \times\left(\frac{-21}{10} \times \frac{-5}{6}\right)$
(iv) $\frac{-12}{5} \times\left(\frac{4}{15} \times \frac{25}{-16}\right)=\left(\frac{-12}{5} \times \frac{4}{15}\right) \times(\ldots \ldots)$
Answer 4:
(i) $\frac{-23}{17} \times \frac{18}{35}=\frac{18}{35} \times \boxed{\frac{-23}{17}}$
(ii) $-38 \times \frac{-7}{9}=\frac{-7}{9} \times \fbox{-38}$
(iii) $\left(\frac{15}{7} \times \frac{-21}{10}\right) \times \frac{-5}{6}=\boxed{\frac{15}{7}} \times\left(\frac{-21}{10} \times \frac{-5}{6}\right)$
(iv) $\frac{-12}{5} \times\left(\frac{4}{15} \times \frac{25}{-16}\right)=\left(\frac{-12}{5} \times \frac{4}{15}\right) \times \boxed{\frac{25}{-16}}$
[∵a×(b×c)=(a×b)×c]
Q5 | Ex-1D | Rational Numbers | Class 8 | RS AGGARWAL | Chapter 1 | myhelper
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Question 5:
Find the multiplicative inverse (i.e., reciprocal) of:
(i)
(ii)
(iii)
(iv) 18
(v) −16
(vi)
(vii) −1
(viii)
(ix)
(x)
Answer 5:
(i) Reciprocal of $\frac{13}{25}$ is $\frac{25}{13}$(ii) Reciprocal of $\frac{-17}{12}$ is $\frac{12}{-17}$, that is, $\frac{-12}{17}$.
(iii) Reciprocal of $\frac{-7}{24}$ is $\frac{24}{-7}$, that is, $\frac{-24}{7}$.
(iv) Reciprocal of 18 is $\frac{1}{18}$
(v) Reciprocal of -16 is $\frac{1}{-16}$, that is, $\frac{-1}{16}$.
(vi) Reciprocal of $\frac{-3}{-5}$ is $\frac{-5}{-3}$, that is, $\frac{5}{3}$
(vii) Reciprocal of-1 is -1.
(viii) Reciprocal of $\frac{0}{2}$ does not exist as $\frac{2}{0}=\infty$
(ix) Reciprocal of $\frac{2}{-5}$ is $\frac{-5}{2}$
(x) Reciprocal of $\frac{-1}{8}$ is -8.
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Q6 | Ex-1D | Rational Numbers | Class 8 | RS AGGARWAL | Chapter 1 | myhelper
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Question 6:
Find the value of:
(i)
(ii)
(iii)
(iv)
Answer 6:
We know that or
Q7 | Ex-1D | Rational Numbers | Class 8 | RS AGGARWAL | Chapter 1 | myhelper
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Question 7:
Verify the following:
(i)
(ii)
(iii)
(iv)
Answer 7:
∴
(iii)
(iv)
Q8 | Ex-1D | Rational Numbers | Class 8 | RS AGGARWAL | Chapter 1 | myhelper
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Question 8:
Name the property of multiplication illustrated by each of the following statements:
(i)
(ii)
(iii)
(iv)
(v)
(vi)
Answer 8:
- Commutative property
- Associative property
- Distributive property
- Property of multiplicative identity
- Property of multiplicative inverse
- Multiplicative property of 0
Q9 | Ex-1D | Rational Numbers | Class 8 | RS AGGARWAL | Chapter 1 | myhelper
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Question 9:
Fill in the blanks:
(i) The product of a rational number and its reciprocal is .......
(ii) Zero has ....... reciprocal.
(iii) The numbers ....... and ....... are their own reciprocals.
(iv) zero is ....... the reciprocal of any number.
(v) The reciprocal of a, where a ≠ 0, is .......
(vi) The reciprocal of , where a ≠ 0, is .......
(vii) The reciprocal of a positive rational rational number is .......
(viii) The reciprocal of a negative rational number is .......
Answer 9:
(i) 1
(ii) no
(iii) 1; -1
(iv) not
(v)
(vi) a
(vii) positive
(viii) negative
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