Question

How many different twotwo​-letter passwords can be formed from the letters

Upper A, Upper B, Upper C, Upper D, Upper E, Upper F, Upper G and Upper H
A, B, C, D, E, F, G and H
if no repetition of letters is​ allowed?

Answer 1

`70`

Explanation:

GIVEN: two two​-letter passwords can be formed from the letters A, B, C, D, E, F, G and H.

TO FIND: How many different two two​-letter passwords can be formed if no repetition of letters is​ allowed.

SOLUTION:

Total number of different letters
`=8`

for two two​-letter passwords
`4` different are required.

Number of ways of selecting
`4` different letters from
`8` letters
`=^8C_4`

`=(8!)/(4!4!)`

`=70`

Hence there are
`70` different two-letter passwords can be formed using
`8` letters.