1. Pettit 9-5 Notes Indicator- D7
9-5 Combinations (pgs )
Indicator- D7

2. Combinations- an arrangement where order does not matter Example 1
How many different two topping pizzas
can be made from 5 toppings?
(Does it matter if you pick pepperoni
then sausage or sausage then pepperoni?)
5C2
Find the permutation of the 5 toppings X4 =20
÷ by the ways to arrange two toppings X1= 2
There are 10 different two topping pizzas.

3. Example 2
Jen can invite three of the 12 girls in her class to a party. How many different arrangements can there be?
(does it matter if you’re picked 1st or 3rd?)
12C3 = 12X11X10 = 1320 = 220 3!
There are 220 different
combinations of girls that
can be invited.

4. How many ways can a president, vice-president and secretary be chosen from the 10 students on student council?
(Are the chances of being president the same as being secretary?)
This is a …….. Permutation
10P3 =10X9X8 = 720 Ways
There are 720 ways to choose officers.

5. Decide if each problem is a permutation or combination then solve.
8 players are playing each other in a checker
tournament. How many games will be played?
8 C 2
How many ways to pick 6 starters from a 12
member volleyball team?
12 C 6
How many ways can you arrange the letters in the word
“word?”
4 P4
W-O-R-D

6. 9-5/ / 7- 22, 27-32