U4 Flashcards
How to use the fundamental counting principle
multiply the number of choices for each stage together
Before finding the number of options for other stages what do you HAVE to do first
Consider any restrictions for a particular stage
Does order matter in permutations
YES
What is the notation for a permutation and what do the variables represent
(sub n)P(sub r)
n= total # of objects r= # of objects chosen
What is the purpose of a factorial
A short way to write a multiplication statement of descending WHOLE numbers
What is “n” an element of
Whole numbers
How do you write (4)(3)(2)(1) as a factorial
4!
Is arranging letters of a word a perm or comb
Perm
Is arranging people in a line a perm or comb
Perm
How do you solve
(sub n) P (sub 2)
1) plug into perm formula
2) expand n! on the top to
n(n-1)(n-2)!
3) cancel the (n-2)! on the bottom and top
4) foils out and factor as a quadratic
Can “n” ever be a negative #
And why
Can’t have a negative amount of objects to pick from
Permutations: how to answer grouped objects questions
1) ask yourself if you can rearrange the group and write that as a factorial (if you can’t continue as usual)
2) ask yourself if you can move the group and write that as just a # (if you can’t continue as usual)
3) how can you rearrange the rest of the positions and write that as a factorial
4) calculate
What is a compliment
And when do we use it
Outcomes that don’t happen
Use it for “not” questions
A group of 2 people don’t want to sit together, what would be the compliment
They do sit together
What is the compliment formula
Not on sheet
Compliment=
(total with no restrictions)-(outcomes that do occur)
Both are written as factorials
What is the formula for permutations with repeated objects
And what do the variables represent
n!/(a! b! c!)
Not on formula sheet
n= # of total objects
a b c= the same of one type (so don’t have to use all of them)
How is VANCOUVER written in the perm formula for repeated objects
9!/ 2!
What formula do square path questions use
Formula for permutations with repeated objects