Question 889622
<pre>
The sample space is not just {heads,tails}.  That would be the sample
space if you were only going to toss the coin one time. Here is the 
sample space:   

{HHHH,<font color="red">HHHT</font>,<font color="red">HHTH</font>,HHTT,<font color="red">HTHH</font>,HTHT,HTTH,HTTT,<font color="red">THHH</font>,THHT,THTH,THTT,TTHH,TTHT,TTTH,TTTT}

I've colored red all the cases that have three heads and 1 tail.

That's 4 out of 16, so the probability is {{{4/16}}} which reduces to {{{1/4}}}

So {{{1/4}}}th of the time on the average you'll get three heads and 1 tail.

Edwin</pre>