Video and ?s Permutations and Combinations

Front

What is a permutation?

Back

A permutation is an arrangement of objects in a specific order. The order matters.

Front

What is a combination?

Back

A combination is a selection of objects where the order does not matter.

Front

What is the formula for permutations of n objects taken r at a time?

Back

The formula is n! / (n - r)!.

Front

What is the formula for combinations of n objects taken r at a time?

Back

The formula is n! / (r! (n - r)!).

Front

When would you use permutations instead of combinations?

Back

Use permutations when the order of selection is important.

Front

When would you use combinations instead of permutations?

Back

Use combinations when the order of selection is not important.

Front

Example of a permutation:

Back

Arranging 3 books on a shelf.

Front

Example of a combination:

Back

Choosing 3 fruits from a basket of 5.

Front

What is the factorial of a number (n!)?

Back

The product of all positive integers up to n.

Front

How many ways can you arrange 4 books on a shelf?

Back

4! = 24 ways.