00:01
Okay, the passwords contain seven characters, and i want to work out how many passwords i can make from these seven characters here, 4bi, 4bi4, 4b4.
00:11
Now, suppose this was 41, 42, 43, in other words, different.
00:19
And here we had b1, b2, i1, i2.
00:24
If they're all different characters, then the answer is easy.
00:29
It's simply 7 factorial.
00:31
Arrange those characters seven factorial different ways.
00:36
I have here seven slots to fill if you like.
00:41
First one i can fill seven ways, then six ways, and five ways, four, three, two, finally one.
00:50
But we have repeats...