123456 these six numbers constitute countless repeated four digits, find out how many groups of numbers 1 is not in a single digit, 6 is not in a thousand digits

123456 these six numbers constitute countless repeated four digits, find out how many groups of numbers 1 is not in a single digit, 6 is not in a thousand digits

If the discussion is divided into different situations, what are the situations?

A seven digit answer with six digits of 123456

Seven digits must be made up of seven digits. It's impossible to use only six digits without repetition;
If the number can be repeated, there are seven possibilities for each digit, and a total of 6 ^ 7 = 279936 possibilities

A seven digit password is composed of five digits. How many possibilities are there for this password
It's not the seventh power of 5, but it must have five digits
Not 10 * 9 * 8 * 7 * 6 = 30240 species --
Is there a more authoritative answer.

12096000
Five numbers are selected for full arrangement
P (10,5) = 30240 species
Then select 2 of them
First, there are five options, four locations
Second, there are four options, five locations
Total: 30240 × (5 × 4) × (4 × 5) = 12096000 species