42.
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 whole numbers, without breaking down the numbers into their 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.)
216 : 40
72 : 22
112 : 32
312 : 82