r-Permutations

Anr-permutationis a sequence of r items with no repetitions, all taken from the same set

1.Passwords

the character in a password is either a digit 0-9 or lowercase letter a-z. How many valid passwords are there with the given restrictions?

• Length is 11.
• No character repeats.
• Must contain: c

is it?

P(11,1)P(35,10)

P(11,1)P(36,10)

P(11,1)P(35,11)

or P(10,1)P(35,11)

2. Formula Usage

what is the result of the following formula:

P(10,7)

is it?

5040

604800

3628800

3.Race Qualifier

A car race qualifier has 10 participants. How many different ways can the top 6cars cross the finish line?

is it

3540

151200

1000000

or 60466176