 Hi and how are you all today? I am Priyanka and let us discuss the following question. Say how many four letter code can be formed using the first ten letters of the English Alphabets if no letter can be repeated. So let us start with our solution. In this question also you will be using the fundamental principle of counting or the multiplication principle. Now we can fill digits in four vacant places. Right? Now in succession by the first ten letters of English Alphabets. So given letters and here also we need to fill in letters and not digits. So given letters are A, B, C, D, E, F, G, H, I, J. Right? These are the first ten letters of English Alphabet. Now for the first place we can fill any of these ten letters. So there are ten different ways of filling up the first place. The second place can be filled up by nine different ways since in the question it is said that no letter can be repeated. Similarly the third place can be filled up by eight different ways and the fourth place can be filled up by seven different ways. So the total number of ways in which these four vacant places can be filled up are ten multiplied by nine multiplied by eight multiplied by seven. That is five zero four zero. And this is our required answer. I hope you enjoyed this session. Do remember your multiplication principle. Bye for now.