How many different words can be formed by taking four letters at a time from the letters of the word "MATHEMATICS" ?
The correct option is A 2454 Here M,A, and T occur twice, rest all words one time. Three cases possible:- CASE 1-All the words are different 8C4×4! CASE 2:-Two same and two different 3C1×7C2×4!2! CASE 3:-Two same of 1st kind and two same of 2nd kind 3C2×4!2!×2! Answer is (CASE 1+CASE 2+CASE 3) =2454