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

Question 15

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.