No, “distinct words” is not the same as “words with distinct letters”. For example “apple”, “banana” and “cherry” are distinct words, but not words with distinct letters.
then is there a difference between “how many 4 letter words can be formed?” and “how many distinct 4 letter words can be formed?” because I am unable to understand the significance of “distinct” here..
Seema, when I say “distinct words” it is just to avoid any possible ambiguity [it is another way of saying “how many different words can I form”. After all, when forming words in English we often use the same word again and again (like I used the word “again” above!)]. I can say BABY and BABA are distinct words (though not words with distinct letters)
CAT-holics 
I don’t understand the (c) part. Why not 5*4*3*2 ?
okay, got it!
in the first question hw many DISTINCT 4 letter words can b formed that means 26*25*24*23 only na hw it came 26^4?
No, “distinct words” is not the same as “words with distinct letters”. For example “apple”, “banana” and “cherry” are distinct words, but not words with distinct letters.
regards
J
then is there a difference between “how many 4 letter words can be formed?” and “how many distinct 4 letter words can be formed?” because I am unable to understand the significance of “distinct” here..
🙂 thank you
Seema, when I say “distinct words” it is just to avoid any possible ambiguity [it is another way of saying “how many different words can I form”. After all, when forming words in English we often use the same word again and again (like I used the word “again” above!)]. I can say BABY and BABA are distinct words (though not words with distinct letters)
regards
J
ok got it..thanks ..