A website requires a 7-digit password. How many different passwords can be made using the digits 0, 1, 2, 3, 4, 5, 6, 7, 8, and 9 if each number can only be used once?
A. 120
B. 70
C.5,040
D. 604,800
Since order matters when making a password, this is a permutation. There are 10 digits to chose from, so we'll start writing our equation like this: 10!/(10-r)! It's a 7 digit password, so we'll write this: 10!/(10-7)! And then solve: 10!/3! 3628800/6 604800 There are 604800 possible passwords, making D the correct answer
