Number analogy section deals with two types of questions:
I. Choosing a similarly related pair as the given number pair on the basis of the relation between the numbers in each pair.
II. Choosing a number similar to a group of numbers on the basis of certain common properties that they possess.
Given set : (21, 51, 15)
Justification: In each set, (3rd number * 2) + 1st number = 2nd number.