MCQ
The number of binary operations on the set {1, 2, 3} is _________?
  • $3^9$
  • B
    $9^3$
  • C
    $27$
  • D
    $3!$

Answer

Correct option: A.
$3^9$
  1. $3^9$
Solution:
Let us denote this set by S, then ∣S∣ = 3.
A binary relation defined on the elements of S maps all elements in S × S to elements in S by definition.
In this case any binary relation will thus have 32 = 9 inputs each of which is an ordered pair of elements from S and only 3 number of possible outputs.
If all possible binary operations are considered then it is possible to assign any of the 3 outputs to any of the 9 inputs. So the number of all binary operations would exactly be $3^9$​​​​​​​.

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