The number of different permutations that can be formed by taking 4 letters at a time from the letters of the word 'REPETITION' is

Step-by-step solution

Given letters are E , E , I , I , T , T , R , P , O , N . Case-I : If all four letters are different then number of four word letters = ^7 P₄=840 Case II : If two letters are same and two letters are different then number of words = ^6 C₂ 4! 2! 3=540 Case-III : If two letters are one type and another two letters are other same type =3 4! 2!2! =18 So, total ways =840+540+18=1398 .