The following problems consists of a set of six figures the first of which is un-numbered and marks, the beginning of series continued in the successive figures numbered from 1 to 5. However, the serise will be established only if the positions of two of the numbered figures are interchanged. The number of the earlier of the two figures is the answer. if no two figures need to be interchanged, then the answer is 5.

Explanation

One line is removed from the figure after every two steps. So, figures (3) and (4) have to be interchanged. Hence answer is 3.