SOLUTION: A biologist needs to determine the number of possible arrangements of 4 kinds of molecules in a chain. If the chain contains 8 molecules with 2 of each kind, how many different arr

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Question 1172261: A biologist needs to determine the number of possible arrangements of 4 kinds of molecules in a chain. If the chain contains 8 molecules with 2 of each kind, how many different arrangements are possible? (2520 arrangements)
Answer by greenestamps(13200) About Me  (Show Source):
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The question is the number of distinguishable arrangements of the letters AABBCCDD.

By a well known counting principle, the number is

8%21%2F%28%282%21%29%282%21%29%282%21%29%282%21%29%29+=+2520