Question #30d1f

1 Answer
Oct 19, 2017

I make it 120 -


You have five odd digits 1,3,5,7,9.

For the first digit in the PIN, you can choose 5 ways.
For each of these, you will have 4 remaining odd digits to choose from - you can choose 4 ways.
Then, for the 3rd digit, you can choose 3 ways from the remaining 3 digits.
For the final digit, you have 2 remaining choices.

So, this makes #5*4*3*2 = 120# different ways to choose a PIN.