Letter series type of questions usually consists of a series of small letters which follow a certain pattern. However, some letters are missing from the series. These missing letters are then given in a proper sequence as one of the alternatives. The candidate is requitred to choose this alternative as the answer.
G4T, J10R, M20P, P43N, S90L
The first letter of each term is moved three steps forward and
the last letter is moved two steps backward to obatin the corresponding letters of the next term.
The numbers follow the sequence x 2 + 1, x 2 + 2, x 2 + 3, x 2 + 4.
So, 10 is wrong and must be replaced by (4 x 2 + 1) i.e. 9.