Question -
Answer -
| LCM | 1 | 2 | 3 | 4 | 5 |
| 1 | 1 | 2 | 3 | 4 | 5 |
| 2 | 2 | 2 | 6 | 4 | 10 |
| 3 | 3 | 5 | 3 | 12 | 15 |
| 4 | 4 | 4 | 12 | 4 | 20 |
| 5 | 5 | 10 | 15 | 20 | 5 |
In the givencomposition table, all the elements are not in the set {1, 2, 3, 4, 5}.
If weconsider a = 2 and b = 3, a * b = LCMof a and b = 6 ∉ {1, 2, 3, 4, 5}.
Thus, * is not abinary operation on {1, 2, 3, 4, 5}.