Tech Tips: Counting

Finding Factorials

To compute $n!$ ...


Finding Combinations

To find ${}_nC_k$, the number of combinations of $n$ things taken $k$ at at time...


Finding Permutations

To find ${}_nP_k$, the number of permutations of $n$ things taken $k$ at a time...


Finding Permutations with Identical Elements

To find the number of ways to arrange $n$ objects when there are $k_1$ identical items of one type, $k_2$ identical items of a second type, $k_3$ identical items of a third type, etc. (where $k_1 + k_2 + k_3 + \cdots = n$) ...