How many 5-letter codes can be formed using the first 7 letters of the English alphabet, if no letters can be repeated?
5040
760
840
2520
Given that,
Forming a five letters code using the first 7 letters of the English alphabet and the repetition of letters is now allowed.
The first place can be filled in 7 different ways by any of the 7 letters of the English alphabet.
The second place can be filled in by any of the remaining letters in 6 different ways.
The third place can be filled in by any of the remaining letters in 5 different ways.
The fourth place can be filled in by any of the remaining letters in 4 different ways.
The fifth place can be filled in by any of the remaining letters in 3 different ways.
Thus, by using the multiplication principle, the required number of ways in which 5-letter code can be filled is
Therefore, the required number of ways in which a 5-letter code can be filled by 2520 ways.
Study 40% syllabus and score up to 100% marks in JEE