Advanced SAT Math Strategies for those that want an 800 in math

[bella1234]

<p>

For example, the number of combinations of {1, 2, 3} taken 2 at a time is 3C2=3!/[2!1!]=3. These combinations are 12, 13, and 23.

</p>

<p>Why is it not 6 just like above permutations problem?</p>