Select the option which is related to fifth number in the same way as second number is related to first number and fourth number is related to third number.

(Note: Numbers must be operated on whole numbers, without dividing them into their constituent digits. For example on 13 - 13 arithmetic operations like addition/subtraction/multiplication etc. can be done in 13. Dividing 13 into 1 and 3 and then doing arithmetic operations on 1 and 3 is not allowed.)

20 : 30 :: 42 : 56 :: 72 : ?

90

20 : 30 :: 42 : 56 :: 72 : ?

The logic followed here is :

20 + 10 = 30

and

42 + 10 + 4

42 + 14 = 56

Similarly

72 + 10 + 4 + 4  

72 + 10 + 8  = 90