So the first digit could be 0-9.
second is the same 0-9
And the 3rd 0-9 and lastly the 4th 0-9
There is a [tex]\frac{1}{10} *\frac{1}{10} *\frac{1}{10}* \frac{1}{10}[/tex] chance that they will get it right by guessing.
So that means a [tex]\frac{1}{10000}[/tex] chance that they will get it right.
So their are 10000 possible codes.
