Question 1183464
<br><pre>
     1  2  3
    ---------
  1) +  +  +
  2) +  +  -
  3) +  -  +
  4) -  +  +
  5) -  -  +
  6) -  +  -
  7) +  -  -
  8) -  -  -</pre>
The 8 outcomes are equally likely, so the probability of each is 1/8.<br>
In 4 of the 8 possible outcomes, 2 or more of the stocks increase in value.  So the probability that at least 2 stocks increase in value is 4/8 = 1/2.<br>
Note that result can be obtained using logical reasoning: for each case where 2 or 3 stocks increase in value, there is an "opposite" case in which 0 or 1 stocks increase in value.  So in exactly half of the cases the number of stocks that increase in value is 2 or more.<br>