Answer:
In a password, symbol/characters can be repeated. first calculate the total
symbols which can be used in a password.
So there are total 26(A-Z),26(a-z),10(0-9) and 2(_,$) symbols.
that is equal to 26+26+10+2=64.
Total number of password of length 4:
here at each place can filled in total number of symbols i.e 64 way for each
place.Then total number of possible password is:
64*64*64*64=16777216
Total number of password of length 5:
here at each place can filled in total number of symbols i.e 64 way for each
place.Then total number of possible password is:
64*64*64*64*64=1073741824
Similarly,
Total number of password of length 6:
64*64*64*64*64*64=68719476736
Total number of password of length 7:
64*64*64*64*64*64*64=4398046511104
Total number of password of length 8:
64*64*64*64*64*64*64=281474976710656
Hence the total number of password possible is:285,942,833,217,536
