Permutations Practice Test 1

If repetitions are allowed, the number of 5 digit numbers formed by 0, 1, 2, 3 and 4 is
* * * * *
4 × 5 × 5 × 5 × 5 = 2500
Number of numbers of 5 digits without repetition = * * * * *
4 × 4 × 3 × 2 × 1 = 96
Hence, the number of numbers in which atleast one digit is repeated = 2500 – 96 = 2404