Question

write all the 2digit number that can be formed by 2,3,4 reputation of digit not allowed​

Answer 1

The number of ways in which hundreds place can be filled = 5 ways. Note: The number of 3-digit numbers formed using the digits 1, 2, 3, 4 and 5 when repetition is not allowed is equivalent to the number of 3 Letter permutations of 5 distinct letter = ${}^{5}{{P}_{3}}=\dfrac{5!}