Question 872360
Look at all of the possible outcomes.
There are {{{2^4}}} or {{{16}}} of them.
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HHHH HHHT HHTH HHTT
HTHH HTHT HTTH HTTT
THHH THHT THTH THTT
TTHH TTHT TTTH TTTT
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1) No heads TTTT {{{P=1/16}}}
2) No tails HHHH {{{P=1/16}}}
3) Exactly 2 heads HHTT HTHT HTTH THHT THTH TTHH {{{P=6/16=3/8}}}