Probability problem dealing with the word INFINITY

[atm]

Hello I would like some help dealing with the following problem as I do not know where to begin.

"Randomly taking 3 letters out of ”INFINITY”, what is the probability that at least2 letters are same?"

Thanks

 

[tkhunny]

Have you examined exactly how many 3-letter "words" there are?

 

[atm]

The number of combinations is 3C8 correct? So then I need to find the combinations of picking atleast two of the same and divide it by the total combinations?

 

[tkhunny]

Would I take the number of letters to the power of 3 for my sample space?

Way too many. Isn't this Without Replacement?