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Rational numbers and their decimal expansions - class-VI

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Say true or false:
The following is a terminating  decimal. $ 5 \div 8$.

  1. True

  2. False


Correct Option: A
Explanation:

A terminating decimal is a decimal that ends. It's a decimal with a finite number of digits.
Here, $5$ divided by $8$ gives $0.625$.

Hence, it is a terminating decimal.

Express the following as a recurring decimal.

$\displaystyle \frac{2}{7}$.

  1. $0.\overline{28}$

  2. $0.\overline{285714}$

  3. $0.\overline{2857}$

  4. None of these


Correct Option: B
Explanation:

$\displaystyle \frac { 2 }{ 7 }  = 0.285714285.. = 0.\overset { \ _ \ _ \ _ \ _ \ _ \ _ \ _ \ _ \ _  }{ 285714 } $

In this division, $285714$ is a recurring decimal.

Express  the following in a recurring decimal form.

$\displaystyle \frac{3}{11}$.

  1. $0.\overline{3}$

  2. $0.\overline{29}$

  3. $0.\overline{4}$

  4. $0.\overline{27}$


Correct Option: D
Explanation:

The value of $\displaystyle \frac { 3 }{ 11 }$ is $ 0.272727272727.. 0.\overset { \ _ \ _ \ _ \ _  }{ 27 } $

In this division $27$ is a recurring decimal.

Find, whether each of the followings is a terminating or a non-terminating decimal.

$7 \div 11$.

  1. Terminating

  2. Non-terminating

  3. Ambiguous

  4. Data insufficient


Correct Option: B
Explanation:

While expressing a fraction in the decimal form, when we perform division we get some remainder. 

If the division process does not end i.e. we do not get the remainder equal to zero; then such decimal is known as non-terminating decimal.
Here, $7$ divided by $11$ gives $0.636363636363.... $.
Therefore, this is a case of non terminating decimal.

Find whether it is a terminating or a non-terminating decimal.

$1.2 \div 0.16$.

  1. Terminating

  2. Non-terminating

  3. Ambiguous

  4. Data insufficient


Correct Option: A
Explanation:

A terminating decimal is a decimal that ends. It's a decimal with a finite number of digits.

$1.2\div 0.16= 7.5$
Hence, terminating decimal.

Express  the following in a recurring decimal form.

$\displaystyle 2\frac{1}{6}$.

  1. $2.1\bar{6}$

  2. $2.1\bar{8}$

  3. $2.1\bar{4}$

  4. $2.1\bar{9}$


Correct Option: A
Explanation:

$2\displaystyle \frac { 1 }{ 6 }  = \frac { 13 }{ 6 }  = 2.166666666.. = 2.1\overset { \ _ \ _  }{ 6 } $

In this division, $6$ is recurring. 

The decimal representation of $\dfrac {65}{455}$ will be

  1. terminating

  2. non-terminating

  3. non-terminating repeating

  4. non-terminating non-repeating


Correct Option: C
Explanation:

$\frac {65}{455}=0.\overline { 142857 } $
Therefore, the decimal representation will be non-terminating repeating.

Convert the following fraction into simple decimal recurring form.

$\displaystyle \frac{5}{6}$ = ?

  1. $0.4\bar 3$

  2. $0.1\bar 3$

  3. $0.\bar 4$

  4. $0.8\bar 3$


Correct Option: D
Explanation:

$\displaystyle \frac { 5 }{ 6 }= 0.83333333..= 0.8\overset { \ _ \ _  }{ 3 } $ 
This is a pure recurring decimal as $3$ is repeated continuously.

The non terminating non-recurring decimal cannot be represented as

  1. irrational numbers

  2. rational numbers

  3. real numbers

  4. none of these


Correct Option: B
Explanation:

Write the decimal number as a fraction $0.2020020002...... $
It is Non- terminating decimal and cannot be represented as a quotient of two integers.
Therefore, B is the correct answer.

Which of the following has a value of non-terminating decimal ?

  1. $\dfrac{7}{4}$

  2. $\dfrac{6}{5}$

  3. $\dfrac{5}{3}$

  4. None of these


Correct Option: C
Explanation:

We know $\dfrac{7}{4}=1.75$

$ \dfrac{6}{5}=1.2$
$ \dfrac{5}{3}=1.6666..$
$\dfrac{5}{3}$ has a  value of non terminating decimal.

If a number has a non-terminating and non-recurring decimal expansion, then it is.

  1. A rational number

  2. A natural number

  3. An irrational number

  4. An integer


Correct Option: C
Explanation:

A number having non-terminating and non-recurring decimal expansion is an Irrational Number


for example 

$\pi$  is an irrational number 

$\pi = 3.1415926535897932384626433832............$


the number has non-terminating decimal expansion and non-recurring.

So option $C $ is correct

$2.13113111311113....$ is _____________.

  1. A rational number

  2. An integer

  3. An irrational number

  4. Not a real number


Correct Option: C
Explanation:

$2.13113111311113....$ follows a definite pattern but the digits after decimal places are non-terminating and non-recurring. 

Hence, number is irrational.

State the following statement is True or False
$\dfrac{7}{9}$ has a value of non terminating decimal number

  1. True

  2. False


Correct Option: A
Explanation:

$\dfrac{7}{9}=0.777...$, Non terminating decimal number.

The decimal expansion of $\sqrt{2}$ is :

  1. finite decimal

  2. 1.4121

  3. non - terminating recurring

  4. non - terminating non recurring


Correct Option: D
Explanation:

Since, $\sqrt { 2 } $ is a irrational number. So, its decimal expansion is non- terminating non recurring. 

So, correct answer is option D.

Classify the decimal form of the given rational number into terminating non-terminating recurring type.

  1. $\dfrac { 13 }{ 5 }$

  2. $\dfrac { 2 }{ 11 }$

  3. $\dfrac { 29 }{ 16 }$

  4. $\dfrac { 17 }{ 125 }$

  5. $\dfrac { 11 }{ 6 }$


Correct Option: A

State the following statement is True or False

$\dfrac {15}{1600}$ has a terminating decimal expansion .

  1. True

  2. False


Correct Option: A
Explanation:

Given, $\displaystyle \frac {15}{1600}= \frac {15}{5^{2}2^{6}}$
As it is in the form of ${ 2 }^{ m }\times { 5 }^{ n }$ where ($n=6,m=2$).
So, the rational number $\displaystyle \frac {15}{1600}$ has a terminating decimal expansion

Without actually performing the long division, state whether the following rational numbers will have a terminating decimal expansion or a non-terminating repeating decimal expansion.
$\dfrac {29}{343}$

  1. Terminating

  2. Non-terminating

  3. Ambiguous

  4. Data insufficient


Correct Option: B
Explanation:

Given, $\displaystyle \frac {29}{343}= \frac {29}{7^{3}}$
As it is not in the form of ${ 2 }^{ m }\times { 5 }^{ n }$.
So, the rational number $\displaystyle \frac {29}{343}$ has a non terminating decimal expansion

If $9{x}^{2}+25{y}^{2}=181$ and $xy=-6$, find the value of $3x+5y$

  1. $\pm 3$

  2. $\pm 1$

  3. $\pm 2$

  4. None of the above


Correct Option: B
Explanation:
Given 

$9{x}^{2}+25{y}^{2}=181$ and $xy=-6$,

formula,
$(a+b)^2=a^2+b^2+2ab$

$\therefore(3x+5y)^2=(3x)^2+(5y)^2+2(3x)(5y)$

$3x+5y=\sqrt{9x^2+25y^2+30xy}$

$=\sqrt{181+30(-6)}$

$=\pm 1$
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