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NCERT Exemplar · Class 8 · Maths

Chapter 1: Rational Numbers

Practice each question, then open the answer or worked solution.

Questions

152 questions
Q71Written answer

1 is the only number which is its own reciprocal.

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Worked solution

Solution:-

False.

Because, the reciprocal of -1 is -1 and reciprocal of 1 is 1.

Q72Written answer

–1 is not the reciprocal of any rational number.

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Worked solution

Solution:-

False.

The reciprocal of-1 is -1.

Q73Written answer

For any rational number x, x + (–1) = –x.

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Worked solution

Solution:-

False.

The correct form is for any rational number x, (x) × (-1) = – x.

Q74Written answer

For rational numbers x and y, if x < y then x – y is a positive rational number.

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Worked solution

Solution:-

False.

Because, for rational numbers x and y, if x < y then x – y is a negative rational number.

Example, let x = 2 and y = 3

Then,

= X – y

= 2 – 3

= -1

Q75Written answer

If x and y are negative rational numbers, then so is x + y.

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Worked solution

Solution:-

True.

For example,

Let x = – 1/3 and y = -2/3

Then,

= x + y

= (-1/3) + (-2/3)

= -1/3 – 2/3

= -3/3

= – 1

Q76Written answer

Between any two rational numbers there are exactly ten rational numbers.

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Worked solution

Solution:-

False.

Between any two rational numbers there are infinite rational numbers.

Q77Written answer

Rational numbers are closed under addition and multiplication but not under subtraction.

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Worked solution

Solution:-

False.

Rational numbers are closed under addition, subtraction and multiplication.

Q78Written answer

Subtraction of rational number is commutative.

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Worked solution

Solution:-

False.

Subtraction of rational number is not commutative.

Let x and y are any two rational number,

Then, x – y ≠ y – x

Q79Written answer

-¾ is smaller than -2.

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Worked solution

Solution:-

False.

Express each of the given rational numbers with 4 as the common denominator.

Now,

-¾ = [(-3×1)/ (4×1)] = (-3/4)

-2/1 = [(-2×4)/ (1×4)] = (-8/4)

Then,

-3/4 > -8/4

Hence,

-¾ > -2

So, -¾ is greater than -2.

Q80Written answer

0 is a rational number.

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Worked solution

Solution:-

True.

Because, 0/1 is a rational number.