00:01
Okay, so how many digits do we have? well, i have zero can be a digit, one, two, all the way up until nine.
00:07
So how many total digits are there? well, one through nine, there's nine, plus the zero, there's a total of 10 digits.
00:13
So for this first idea, okay, how many possible digits are there in the first place? okay, so it can't be zero, because then it wouldn't be a five digit number.
00:25
So it has to be a total of nine possible digits that's left.
00:29
Okay, the second digit.
00:32
It can't be the same as the first digit.
00:35
So there's 10 digits, right? it can be zero here, minus one.
00:38
Whatever the first digit is, there's nine other possibilities.
00:42
The third digit.
00:43
Okay, so it can't be the same as the second.
00:46
I have 10 digits, so i'm going to subtract one, whatever the second digit is...