00:01
In this question, we're given that a computer password is eight characters long and consists of one letter followed by seven digits.
00:10
And the digits cannot be repeated.
00:12
Now, a number of possible passwords.
00:14
Now, before we answer this, always ask yourself, after you have chosen the digits and all that, it's order important.
00:22
Now, we know the password order is important.
00:25
The same numbers or same digits, if they are arranged in a different order, it will be.
00:31
A different password.
00:33
So order is important.
00:34
Now if order is important, we will be using permutation.
00:41
If order is not important, we will use combination.
00:45
So in this case, it's permutation...