Q11Multiple choice
If x + 0 = 0 + x = x, which is rational number, then 0 is called
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Worked solution
Solution:-
(a) identity for addition of rational numbers.
NCERT Exemplar · Class 8 · Maths
Chapter 1: Rational Numbers
Practice each question, then open the answer or worked solution.
Questions
152 questionsQ12Written answer
To get the product 1, we should multiply (8/21) by
(a) 8/21 (b) -8/21 (c) 21/8 (d) -21/8
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Worked solution
Solution:-
(c) 21/8
Because,
= (8/21) × (21/8)
= (8 × 21) / (21 × 8)
= 168/168
= 1
Q13Written answer
– (-x) is same as
(a) –x (b) x (c) 1/x (d) -1/x
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Worked solution
Solution:-
(b) x
We know that, (- × – = +)
Q14Written answer
The multiplicative inverse of 
is
(a) 8/7 (b) -8/7 (c) 7/8 (d) 7/-8
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Worked solution
Solution:-
(d) 7/-8
= 
= – 8/7
= 7/-8 [∵ reciprocal]
Q15Written answer
If x be any rational number then x + 0 is equal to
(a) x (b) 0 (c) –x (d) Not defined
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Worked solution
Solution:-
(a) x
= x + 0 = x [∵ identity for addition of rational numbers]
Q16Written answer
The reciprocal of 1 is
(a) 1 (b) -1 (c) 0 (d) Not defined
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Worked solution
Solution:-
(a) 1
Reciprocal of 1 = 1/1
= 1
Q17Written answer
The reciprocal of -1 is
(a) 1 (b) -1 (c) 0 (d) Not defined
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Worked solution
Solution:-
(b) -1
Reciprocal of -1 = -1/1
= -1
Q18Written answer
The reciprocal of 0 is
(a) 1 (b) -1 (c) 0 (d) Not defined
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Worked solution
Solution:-
(d) Not defined
Reciprocal of 0 = 1/0
= not defined
Q19Written answer
The reciprocal of any rational number p/q, where p and q are integers and q ≠ 0, is
(a) p/q (b) 1 (c) 0 (d) q/p
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Worked solution
Solution:-
(d) q/p
The reciprocal of p/q = q/p
Q20Written answer
If y be the reciprocal of rational number x, then the reciprocal of y will be
(a) x (b) y (c) x/y (d) y/x
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Worked solution
Solution:-
(a) x
If y be the reciprocal of rational number x, i.e. y = 1/x
x = 1/y
Then,
Reciprocal of y = x