I am trying to understand the possible number of combinations for two specific people (let's call them Person A and Person B) to be put in the same group of 3 if there are 39 total people to sort into groups of 3.
My understanding is that with a total group of 39 people, there are 9,880 possible combinations for putting those 39 people into groups of 3. However, this added criteria of the odds of two specific people, Person A and Person B, being put in the same group of 3 is difficult for me to understand how to calculate.
Any help would be much appreciated!!
The simplest way to compute it is to imagine $39$ slots split into $13$ groups of $3$
Person $A$ can be put in any slot. for person $B$ to be in the same group as $A$, there are $2$ vacant slots out of $38$ remaining,
Thus P($A$ and $B$ are in same group) $=\Large\frac2{38} = \frac1{19}$