Question

How many four-letter codes can be made if no letter can be used twice?

Answer 1

solution given:

total alphabet =26

The first letter can be any one of the 26 letters in the alphabet.

so

1st word =26letter

since no word is repeated

2nd word =25letter

3rd word=24letter

4th word=23letter

so

four-letter code =26×25×25×23=358800codes

so

358800codes of four-letter codes can be made if no letter can be used twice.

Answer 2

There are 26 letters in the alphabet.

1st letter can be 1 of 26

2nd letter can be 1 of 25

3rd letter can be 1 of 24

4th letter can be 1 of 23

Total combinations = 26 x 25 x 24 x 23 = 358,800