Four number-pairs have been given, out of which three are alike in some manner and one is different. Select the one that is different.
(NOTE: Operations should be performed on the whole numbers, without breaking down the mumbers into its constituent digits. E.g. 13 - Operations on 13 such as adding/subtracting/multiplying etc. to 13 can be performed. Breaking down 13 into 1 and 3 and then performing mathematical operations on 1 and 3 is not allowed.)
15 ∶ 126
27 ∶ 234
31 ∶ 270
17 ∶ 162
1
17 ∶ 162
2
15 ∶ 126
3
27 ∶ 234
4
31 ∶ 270