Correct Answer - Option 2 : 51
Given,
3978 ∶ 72 ∶∶ 5172 ∶ ?
The pattern followed here is,
3978 = 3 + 9 + 7 + 8 = 27
Arrange the above addition in reverse order,
∴ 27 = 72
Similarly,
5172 = 5 + 1 + 7 + 2 = 15
Arrange the above addition in reverse order,
∴ 15 = 51
Hence, the correct answer is 51.