NCERT Exemplar Solutions
Class 7 - Mathematics - Unit 1: Number System - Multiple Choice Questions
Question 15

Question.  15

Which of the following is the multiplicative identity for an integer \(a\)?

(a)

\(a\)

(b)

1

(c)

0

(d)

–1

Detailed Answer with Explanation:

Why (b) 1 is correct

  1. “Multiplicative identity” means a number that keeps any number the same when we multiply by it.
  2. Take any integer (a).

  3. (a imes 1 = a)

  4. So, multiplying by 1 does not change the value. Hence, 1 is the multiplicative identity.

Why the other options are not correct

  • (a) (a):

    (a imes a = a^{2})

    This is usually not equal to (a) (except for special cases like (a=0) or (a=1)).
  • (c) 0:

    (a imes 0 = 0)

    This changes the number to zero, so it does not keep it the same.
  • (d) –1:

    (a imes (-1) = -a)

    This flips the sign, so the value changes.

Therefore, the multiplicative identity is 1.

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