Question

A special type of password consists of 3 different letters of the alphabet, and the two different numbers, where each letter and each number is used only once. How many different possible passwords are there?

Answer 1

There can be 14,040,000 different passwords

Explanation:

Number of permutations to order 3 letters and 2 numbers (total 5)

(AAANN, AANNA,AANAN,...)

= 5! / (3! 2!)

= 120 / (6*2)

= 10

For each permutation, the three distinct (English) letters can be arranged in

26!/(26-3)! = 26!/23! = 26*25*24 = 15600 ways

For each permutation, the two distinct digits can be arranged in

10!/(10-2)! = 10!/8! = 10*9 = 90 ways.

So the total number of distinct passwords is the product of all three permutations,

N = 10 * 15600 * 90 = 14,040,000