3 Algebra II
Notes 12.2 Combinations
Combinations – a combination of “r” objects taken from a group of “n” objects happens when the
ORDER that the objects chosen does not matter.
Examples of COMBINATIONS:
1.) Choosing a committee from a group.
2.) Choosing toppings for a sundae, pizza, sandwich, etc.
3.) Picking cards from a deck to form a hand.
Formula for Combinations:
nCr=
n!
r !( n − r ) !
n = total number of objects and
r = number for the subset.
Ex: Find each combination.
a.)
5
C3
b.)
8
C8
c.)
4
C1
d.) From a group of 20 volunteers, you must choose 18 to be peer counselors. How many different
ways can this be done?
e.) From a group of 20 volunteers, you must choose AT LEAST 18 to be peer counselors. How many
different ways can this be done?
f.) Friendly’s Restaurant has 10 different toppings to choose from for their classic sundae. How many
three-topping classic sundaes can be made?
Assign p. 712 – 713 #18 – 25, 47 – 50, 55 – 58
Assign Wkst 12.2 A