A 7character password consists of three numbers from 2 to 9

A 7-character password consists of three numbers (from 2 to 9) followed by four letters (from A to N).

a) How many different passwords can be formed that have no repeated number or letters?

b) How many different passwords can be formed if letters and numbers can be repeated?

Solution

a) Different passwords can be formed that have no repeated number or letters:

= ( 8*7*6) * (14*13*12*11)

= 8072064 Answer

b) Different passwords can be formed if letters and numbers can be repeated:

= ( 8*8*8) * (14*14*14*14)

= 19668992 Answer