Question 1128752
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<pre>
For 3 children, there are  {{{2^3}}} = 8 possibilities of their gender combinations.


Of them, there are only two to have all three children of the same gender:  BBB  and/or  GGG
(B = Boy, G = girl).


Hence, the probability to have all three children of the same gender is  {{{2/8}}} = {{{1/4}}}.    


Then the probability NOT to have all three children of the same gender is the complement to it, i.e.  1 - {{{1/4}}} = {{{3/4}}}.     <U>ANSWER</U>
</pre>

Thanks to tutor @greenestamps for correction.