MCQ
Number of binary operations on the set $\{a, b\}$ are:
  • A
    $10$
  • $16$
  • C
    $20$
  • D
    $8.$

Answer

Correct option: B.
$16$
A binary operation $^*$ on $\{a, b\}$ is a function from $\{a, b\} \times \{a, b\} \rightarrow \{a, b\}$
i.e., $^*$ is a function from $\{(a, a), (a, b), (b, a), (b, b)\}.$
Hence, the total number of binary operations on the set $\{a, b\}$ is $2^4$ i.e., $16.$
The correct answer is $B.$

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