The number of 4-digit numbers that can be made with the digits 1, 2, 3, 4, 5 in which at least two digits are identical is
45 - 5!
505
600
None of these
As learnt in concept
Factorial Notation -
The product of first n natural numbers. n! = n(n - 1) (n - 2) ..........3 . 2 . 1
- wherein
Where
digits are 1, 2, 3, 4, 5
Total number of 4 digits numbers = 5 X 5 X 5 X 5
Numbers with no identical digits =5!=120
Thus, required number =625-120=505
Option 1)
45 - 5!
This is incorrect option
Option 2)
505
This is correct option
Option 3)
600
This is incorrect option
Option 4)
None of these
This is incorrect option