The logic is 5*5+5=30, then 30*5+5=155, and so on we get 780*5+5=3905
Since Nithya and Suganya exchange places, so Rita’s new position is the same as Monika’s earlier position. This position is 17th from the right and 10th from the left. Therefore Number of girls in the row = (16 + 1 + 9) = 26.