Question

Abby is registering at a Web site. She must select a password
containing six numerals to be able to use the site. How many passwords are
allowed if no digit may be used more than once?

Answer 1

This time it does indeed involve permutations. Assuming by numerals they mean 0-9 it would be 10P6

Answer 2

Six digits not 4

Answer 3

\[\frac{10!}{(10-6)!} = 151200\]

Answer 4

you have 10 possibilities for the first number so 10
because you already used one digit, you will only have 9 possibilities for your second choice
in the third one you would have 8
fourth 7
fifth 6
and sixth 5
therefore your answer would be 10*9*8*7*6*5