# Permutation and Combination

• September 28th 2008, 07:03 AM
magentarita
Permutation and Combination
Can someone explain the basic difference between permutation and combination?

Are there a formula(s) to know?

• September 28th 2008, 07:34 AM
Plato
Quote:

Originally Posted by magentarita
Can someone explain the basic difference between permutation and combination?

Permutations are order driven: the number of ways to form a queue.
Combinations are content driven: the number of ways to form a collection.

Quote:

Originally Posted by magentarita
Are there a formula(s) to know?

$P\left( {N,k} \right) = \frac{{N!}}{{\left( {N - k} \right)!}} = N(N - 1)(N - 2) \cdots (N - k + 1)$

$C(N,k) = {{N} \choose {k}}= \frac{{N!}}{{k!\left( {N - k} \right)!}}$
• September 28th 2008, 09:37 PM
magentarita
great notes
Quote:

Originally Posted by Plato
Permutations are order driven: the number of ways to form a queue.
Combinations are content driven: the number of ways to form a collection.

$P\left( {N,k} \right) = \frac{{N!}}{{\left( {N - k} \right)!}} = N(N - 1)(N - 2) \cdots (N - k + 1)$

$C(N,k) = {{N} \choose {k}}= \frac{{N!}}{{k!\left( {N - k} \right)!}}$

Thank you for the great formulas and definitions.