<p>What's a mathematical way to find all the possible combinations of 3s for 5 different toys? I would like some sort of equation or standard rule that can be applied to all problems like this, please.</p>

<p>Permutations.</p>

<p>Three spots: five choices for the first spot x 4 choices for the second x 3 choices for the third spot.</p>

<p>make 3 lines, since you have 3 spots _ _ _

the 1st spot you have 5 choices

the 2nd spot you only have 4, since one was used

and the 3rd spot you have 3

5 4 3

¯ ¯ ¯

and multiply them.. 5 x 4 x 3</p>

<p>hope that helped</p>

<p>Name them A,B,C,D,E and write out all possible subgroups.

If order of toys is not important, then:

ABC

ABD

ABE

ACD (why not ACB ?)

...</p>

<p>See a pattern?</p>