I'm taking a crack at learning probability and statistics starting from the basics. Anyways here is the question.(adsbygoogle = window.adsbygoogle || []).push({});

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A fair coin is tossed 10 times and the sequence of scores recorded.

How many sequences are there?

How many sequences are there that contain exactly 3 heads?

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The first one is no problem. I understand it. It simply is 2^10 = 1024 possible sequences.

The second one is the one i have trouble dealing with. How do you compute it with that special case added in? The answer given is 120.

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