Question

Determine the number of natural number smaller than 104, in the decimal notation of which all the digits are distinct

Answer 1

Step-by-step explanation:

It means that that you must find all numbers in the range 1≤n<104 without duplicate digits in their decimal notation. In some schools the range of "natural number" is 0≤n<104.

1234

is allowed but not

1134

because it contains a repetition.