Q:

Three of the following four triads are alike in a certain way as they are formed by performing the same mathematical operations among themselves and thus form a group. Which triad does NOT belong to that group?

• 1
  11 : 21: 121
• 2
  7 : 15: 49
• 3
  2 : 3: 4
• 4
  9 : 17: 81