SOLUTION: A PIN code has 3 letters. How many different PIN codes are possible if 3 of the same letter are not allowed (like AAA), but two of the same are allowed (AAB,ABA and BAA)?

SOLUTION: A PIN code has 3 letters. How many different PIN codes are possible if 3 of the same letter are not allowed (like AAA), but two of the same are allowed (AAB,ABA and BAA)?

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Question 278532: A PIN code has 3 letters. How many different PIN codes are possible if 3 of the same letter are not allowed (like AAA), but two of the same are allowed (AAB,ABA and BAA)?
Answer by nyc_function(2741) (Show Source): You can put this solution on YOUR website!
Let's use AAB.
3P3 = 3!/(3 - 3)!
3P3 = 6/0!
3P3 = 6/1
3P3 = 6 different PIN codes are possible.
Or you can do it the long way.
AAB becomes AA, AB, BA = 2 letters + 2 letters + 2 letters = 6 letters or PINS.
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