Combinations
Example
A coffee shop serves 12 different kinds of coffee drinks. How many ways can 4 different coffee drinks be selected?
Step 1:
Since we see that there is no significance to ordering these drinks we are using combinations
Step 2:
Now we calculate
\[_{12}C_4=\frac{_{12}P_4}{4!}=\frac{12\cdot 11\cdot 10\cdot 9}{4\cdot 3\cdot 2\cdot 1}=495\]