9-5 Combinations

Find the number of combinations of a set of objects

Ex) We want to choose a committee of 2 from 4 people. How

many ways to do this?

• Demonstrate using volunteers.

Coach Smith wants to select co-captains for her basketball team.

She will select two girls from the four oldest members on the team: Amber, Danielle, Leah, and Emma

1. Use the first letter of each name to list all of the permutations of co-captains. How many are there?

2. Cross out any arrangement that contains the same letters as another one in the list. How many are there now?

3. Explain the difference between the two lists above.

Combination

• An arrangement, or listing, of objects in which order is not important.

• For example, choosing Emma and Amber is the same as choosing Amber and Emma.

4 players taken 2 at a time.

4*3

2!

Ex) Committee of 4 from 10

Choose 3 movies from 26 movies

Choosing 5 shirts for a trip from 10 in all.

Choosing 5 cards from a deck of 52

Select 3 toppings to go on pizza from 13 different toppings

Paul’s Pizza Parlor is offering a large two-topping pizza for $14.99. There

are five toppings from which to choose. How many different two-topping pizzas

are possible?

A checkers tournament features each of the top 8 regional players playing

every opponent one time. The 2 players with the best records will then play in a final round to determine the

champion. How many matches will be played if there are no ties?

With a partnerHandout—right side only

Combination Code

Journal

• In a t-table—describe two situations in which order of selection is important and when order is not important.

P 389: 1, 3-16, 19