In the following number-pairs, the second number is obtained by applying certain mathematical operations to the first number. Select the number-pair in which the numbers are related in the same way as are the numbers of the following number-pairs. (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.)
21, 105
19, 95
A13, 95
B24, 65
C14, 70
D31, 90