Permutations and Combinations
How many digit mobile numbers can be formed if at least one digit is repeated?
Correct Answer: Option(d)
At least one digit is repeated Total No. digit is repeated
For total permutations,
Any of the digit can be filled by any of the numbers.
For no digit to be repeated:
Let first digit be any of the numbers,
Next digit can be any of the remaining and so on.....
Hence, the answer is