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 numbers 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.)
29 : 160
31 : 138
27 :150
21 : 120
Show answer & explanation
Correct answer: A
Explanation
The correct answer is option 1 i.e. 31 : 138.
29 : 160 → 29 × 5 + 15 = 145 + 15 = 160
31 : 138 → 31 × 5 − 17 = 155 − 17 = 138
27∶150 → 27 × 5 + 15 = 135 + 15 = 150
21: 120 → 21 × 5 + 15 = 105 + 15 = 120
Except for 31: 138 all are follow the same logic.