12.3 Permutations and
Combinations
Mrs. Taormina
Probability and Statistics
Permutations
and
Combinations
What’s the Difference?
"My fruit salad is a combination of apples,
grapes and bananas" We don't care what
order the fruits are in, they could also be
"bananas, grapes and apples" or "grapes,
apples and bananas", its the same fruit salad.
(order does not matter) Combination
What’s the Difference?
"The combination to the safe was 472". Now
we do care about the order. "724" would not
work, nor would "247". It has to be exactly 47-2.
(Order matters) Permutation
This should be called a
“permutation” lock!
(You can laugh…ha! ha!)
Factorial !
7 ! = 7 x 6 x 5 x 4 x 3 x 2 x 1 = 5040
3!=3x2x1=6
On Calculator:
MATH
PRB
! (#4)
Permutations
• This formula is used for permutations without
repetition. (The FCP took care of repetition).
Number of items
How many we
are choosing
Combinations
• This formula is used for combinations without
repetition.
Number of items
How many we
are choosing at
a time
Pascal’s Triangle
C(0, 0)=1
C(1, 0)=1 C(1,1)=1
C(2, 0)=1 C(2,1)=2 C(2,2)=1
C(3, __) etc.
C(4, __)
C(5, __)
ASSIGNMENT:
Pg. 708 #7-56
(Tuesday and Wednesday)
Calculator Steps:
Enter n MATH PRB (#2-nPr) or (#3-nCr) enter r
Today at 2:00 p.m. we will be having a tornado
drill. Our class must sit together in the science
hallway. (Single row, sitting towards the wall, not
in front of glass, with your head covered)