Quiz - 1 Class - 9 Chapter - Number System

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• 1.

0.1 can be represented by

• A.

1/10

• B.

1/100

• C.

1/1000

• D.

1/10000

A. 1/10
Explanation
The decimal number 0.1 can be represented as 1/10 because the decimal point separates the whole number part from the fractional part. In this case, the fractional part is 1/10, which means that there is one tenth of a whole.

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• 2.

Which one of the following is a correct statement?

• A.

Decimal expansion of a rational number is terminating.

• B.

Decimal expansion of a rational number is non-terminating.

• C.

Decimal expansion of an irrational number is terminating.

• D.

Decimal expansion of an irrational number is non- terminating and non- repeating.

D. Decimal expansion of an irrational number is non- terminating and non- repeating.
Explanation
The decimal expansion of an irrational number is non-terminating and non-repeating because irrational numbers cannot be expressed as a fraction or a ratio of two integers. Therefore, their decimal representation continues indefinitely without any pattern or repetition. Examples of irrational numbers include âˆš2, Ï€, and e.

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• 3.

Which one of the following statements is true?

• A.

The sum of two irrational numbers is always an irrational number.

• B.

The sum of two irrational numbers is always a rational number.

• C.

The sum of two irrational numbers may be a rational number or an irrational number.

• D.

The sum of two irrational numbers is always an integer.

C. The sum of two irrational numbers may be a rational number or an irrational number.
Explanation
The statement "The sum of two irrational numbers may be a rational number or an irrational number" is true because when two irrational numbers are added together, the result can either be a rational number or an irrational number. This is because the irrational numbers can have infinite non-repeating decimal places, and when added together, the decimal places may either cancel out to form a rational number or continue to be non-repeating to form an irrational number.

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• 4.

Which of the following is a correct statement ?

• A.

Product of two irrational numbers is always irrational.

• B.

Product of a rational and an irrational number is a always irrational.

• C.

Sum of two irrational numbers can never be irrational.

• D.

Sum of an integer and a rational number can never be an integer.

B. Product of a rational and an irrational number is a always irrational.
Explanation
The statement "Product of a rational and an irrational number is always irrational" is correct. This can be proven by considering the definition of rational and irrational numbers. A rational number can be expressed as a fraction, where the numerator and denominator are integers. An irrational number cannot be expressed as a fraction and has an infinite non-repeating decimal representation. When we multiply a rational number with an irrational number, the result will always be irrational because the product of a rational number and a non-zero irrational number cannot be expressed as a fraction and will have an infinite non-repeating decimal representation.

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• 5.

Which of these is greatest number?

• A.

0.1

• B.

0.01

• C.

0.001

• D.

0.0001

A. 0.1
Explanation
The given numbers are all decimal numbers, and to determine the greatest number, we need to compare their values. Among the given options, 0.1 is the largest number because it has the largest place value. The number 0.1 is greater than 0.01, 0.001, and 0.0001 as it has a larger digit in the tenths place compared to the other numbers.

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• 6.

The number 0.318564318564318564.......... is

• A.

A natural number

• B.

An integer

• C.

A rational number

• D.

An irrational number

C. A rational number
Explanation
The number 0.318564318564318564... is a rational number because it can be expressed as a fraction of two integers. The pattern of repeating digits indicates that the number can be written as 318564/999999, which is a ratio of two integers and therefore a rational number.

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• 7.

if n is a natural number then, √n is always

• A.

Always a natural number

• B.

Always an irrational number

• C.

Always an irrational number

• D.

Sometimes a natural number and sometimes an irrational number

D. Sometimes a natural number and sometimes an irrational number
Explanation
The square root of a natural number n can be either a natural number or an irrational number. For example, the square root of 4 is 2, which is a natural number. However, the square root of 2 is an irrational number because it cannot be expressed as a fraction. Therefore, the statement "sometimes a natural number and sometimes an irrational number" is correct.

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• 8.

Which of the following numbers can be represented as non-terminating, repeating decimals?

• A.

39/24

• B.

3/16

• C.

3/11

• D.

137/25

C. 3/11
Explanation
The number 3/11 can be represented as a non-terminating, repeating decimal because when we divide 3 by 11, the result is 0.272727... The decimal part, 0.27, repeats infinitely. Therefore, 3/11 can be represented as a non-terminating, repeating decimal.

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• 9.

Every point on a number line represents

• A.

A unique real number

• B.

A natural number

• C.

A rational number

• D.

An irrational number

A. A unique real number
Explanation
Every point on a number line corresponds to a specific position or value, and since real numbers include both rational and irrational numbers, each point on the number line represents a unique real number. Real numbers encompass all possible values on the number line, making this the correct answer.

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• 10.

The number 1.272727...... in the form p/q, where p and q are integers and q is not zero, is

• A.

14/9

• B.

14/11

• C.

14/13

• D.

14/15

B. 14/11
Explanation
The number 1.272727... can be expressed as a repeating decimal. To convert it into a fraction, we can let x = 1.272727... and subtracting it from 100x gives us 100x - x = 127.272727... - 1.272727... = 126. Thus, 99x = 126 and dividing both sides by 99 gives us x = 14/11. Therefore, the fraction representation of 1.272727... is 14/11.

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• 11.

The number 0.333333...... in the form p/q, where p and q are integrals and q is not zero, is

• A.

33/100

• B.

3/10

• C.

1/3

• D.

3/100

C. 1/3
Explanation
The number 0.333333... can be expressed as a fraction in the form p/q, where p and q are integers and q is not zero. In this case, the repeating decimal 0.333333... can be written as 1/3. This is because the decimal representation of 1/3 is 0.333333..., where the digit 3 repeats indefinitely. Therefore, the correct answer is 1/3.

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• 12.

The smallest rational number by which 1/3 should be multiplied so that its decimal expansion terminates after one place of decimal, is

• A.

1/10

• B.

3/10

• C.

3

• D.

30

B. 3/10
Explanation
To find the smallest rational number by which 1/3 should be multiplied so that its decimal expansion terminates after one place of decimal, we need to convert 1/3 into a decimal. When we divide 1 by 3, we get 0.3333... which is a non-terminating decimal. To make it terminate after one place of decimal, we need to multiply 1/3 by 10. This gives us 10/3 which is equal to 3 1/3. However, the question asks for the smallest rational number, so we simplify 10/3 to 3/10, which is the correct answer.

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• 13.

0.32222222...... when expressed in the form p/q( where p and q are integers and q is not zero)

• A.

8/25

• B.

29/90

• C.

32/99

• D.

32/199

B. 29/90
Explanation
The given decimal number, 0.32222222......, can be expressed as a fraction in the form p/q. To find the fraction, we can let x = 0.32222222...... and subtract it from 10x. This gives us 10x - x = 9x, and 9x = 3.2222222...... Subtracting x from this equation, we get 9x - x = 3.2222222...... - 0.32222222......, which simplifies to 8x = 3. Subtracting x from both sides, we have 8x - x = 3 - 0.32222222......, which simplifies to 7x = 2.6777777...... Dividing both sides by 7, we get x = 2.6777777...... / 7. Simplifying this fraction, we have x = 0.3825396825......, which can be written as the fraction 29/90. Therefore, the correct answer is 29/90.

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• 14.

Which of the following is irrational ?

• A.

0.15

• B.

0.01516

• C.

0.151615161516.....

• D.

0.50155001500015....

D. 0.50155001500015....
Explanation
The number 0.50155001500015.... is irrational because it is a non-repeating, non-terminating decimal. Irrational numbers cannot be expressed as a fraction and have an infinite number of non-repeating decimal places.

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• 15.

The value of 0.232323..... + 0.222222........ is

• A.

0.45454545.....

• B.

0.43434343

• C.

0.45

• D.

0.43

A. 0.45454545.....
Explanation
The given question asks for the sum of two repeating decimals, 0.232323..... and 0.222222..... To find the sum, we can add the corresponding digits of each decimal place. Starting from the rightmost digit, we add 3 and 2, which gives us 5. Moving to the next decimal place, we add 2 and 2, which gives us 4. Continuing this pattern, we find that the sum of the two decimals is 0.45454545..... Therefore, the correct answer is 0.45454545.....

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