SOLUTION: In how many three-digit numbers are at least two of the digits the same?

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Question 839174: In how many three-digit numbers are at least two of the digits the same?
Answer by Edwin McCravy(20056)   (Show Source): You can put this solution on YOUR website!
They all have either exactly 2 or all 3 digits the same.

There are 9 3-digit number with all 3 digits the same, 111,222,...999. 

The 3-digit numbers with exactly 2 digits the same are all of the form 
ABA, AAB, or ABB. (For example 575, 557, or 577)

Therefore, we can choose the form in 3 ways.
For each of those forms the A can be chosen 9 ways (A can't be 0).
Then B can be chosen 9 ways (B can't be the same digit as A, 
but B can be 0)

Answer: 9+3󭘹 = 9+243 = 252 possible 3-digit numbers with at least
2 digits the same.

Edwin
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