Question

1: How many passwords you can make using the letters in the word "COFFEE"?

2: How many 12-digit Hexadecimal numbers end in 55AA?

Answer 1

1:

Here we need to find the number of permutation of word COFFEE. There are 6 letters out of which 2 are F and 2 are E so the possible permutations are

Hence, possible number of different passwords is 180.

2:

There are 0-9 that is 10 digits and A to F letters in hexa decimal system Lats four digits are fixed to 55AA. Rest 8 digits can be selected in 16 ways each so possible number of 12 digit Hexadecimal numbers end in 55AA is

16 *16*16*16*16*16*16*16 = 4,294,967,296