A special type of password consists of four different letter

A special type of password consists of four different letters of the alphabet, where each letter is used only once. How many different possible passwords are there?

Solution

No .of different possible passwords are that consists of four diffrent letters of the aplphabet is 26 * 25 * 24 * 23 = 358800 , becuase count of alphabets are 26, we have 4 blanks to fill. the first blank can be filled with 36 possiblities , 2nd be 26-1 = 25 because a letter has been filled in the first blank ... so on for the next blanks