Combinations

Front

What is a combination?

Back

A combination is a selection of items from a larger set where the order does not matter.

Front

What is a permutation?

Back

A permutation is an arrangement of items from a larger set where the order does matter.

Front

When would you use combinations instead of permutations?

Back

Use combinations when the order of selection does not matter, such as choosing members for a committee.

Front

How many combinations can be formed from 4 letters A, B, C, D?

Back

There are 5 combinations of 4 letters from A, B, C, D.

Front

What is the formula for combinations?

Back

The formula for combinations is C(n, r) = n! / (r!(n-r)!), where n is the total number of items, and r is the number of items to choose.

Front

What is the formula for permutations?

Back

The formula for permutations is P(n, r) = n! / (n-r)!, where n is the total number of items, and r is the number of items to arrange.

Front

Example of a combination problem: Choose 4 students from a class of 10. How many ways can this be done?

Back

C(10, 4) = 210 ways.

Front

Example of a permutation problem: How many ways can you arrange 3 books on a shelf?

Back

P(3, 3) = 6 ways.

Front

What is the difference between combinations and permutations?

Back

The difference is that combinations do not consider order, while permutations do.

Front

In how many ways can a teacher pair 20 students?

Back

There are 190 ways to pair 20 students.