Three of the following four are alike in a certain way and thus form a group. Which is the one that does NOT belong to that group?
(1) 4-125
(2) 3-64
(3) 2-8
(4) 6-343

Four number-pairs are given, three follow a pattern. Choose the odd pair.

Find the odd one out.

Four number-sets have been given, out of which three are alike in some manner and one is different. Select the number-set 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.)

In three of the following four number pairs, the numbers are related in the same way and thus form a group. Which number pair DOES NOT belong to that group? 
(NOTE: Operations should be performed on the whole numbers, without breaking down the numbers into their constituent digits. E.g. 13 – Operations on 13 such as adding / subtracting /multiplying to 13 can be performed. Breaking down 13 into 1 and 3 and then performing mathematical operations on 1 and 3 is not allowed.)