Difference between revisions of "Georgeooga-Harryooga Theorem"

(Proof 1)
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Let our group of <math>a</math> objects be represented like so <math>1</math>, <math>2</math>, <math>3</math>, ..., <math>a-1</math>, <math>a</math>. Let the last <math>b</math> objects be the ones we can't have together.
 
Let our group of <math>a</math> objects be represented like so <math>1</math>, <math>2</math>, <math>3</math>, ..., <math>a-1</math>, <math>a</math>. Let the last <math>b</math> objects be the ones we can't have together.
  
Then we can organize our objects like so <math>1\square2\square3\square...\square a-b-1\square a-b</math>
+
Then we can organize our objects like so <math>\square1\square2\square3\square...\square a-b-1\square a-b\square</math>
  
 
We have <math>(a-b)!</math> ways to arrange the objects in that list.
 
We have <math>(a-b)!</math> ways to arrange the objects in that list.

Revision as of 10:15, 18 November 2020

Definition

The Georgeooga-Harryooga Theorem states that if you have $a$ distinguishable objects and $b$ of them cannot be together, then there are $\frac{(a-b)!(a-b+1)!}{(a-2b+1)!}$ ways to arrange the objects.


Created by George and Harry of The Ooga Booga Tribe of The Caveman Society

Proofs

Proof 1

Let our group of $a$ objects be represented like so $1$, $2$, $3$, ..., $a-1$, $a$. Let the last $b$ objects be the ones we can't have together.

Then we can organize our objects like so $\square1\square2\square3\square...\square a-b-1\square a-b\square$

We have $(a-b)!$ ways to arrange the objects in that list.

Now we have $a-b+1$ blanks so we have $_{a-b+1}P_{b}=\frac{(a-b+1)!}{(a-2b+1)!}$ ways to arrange the objects we can't put together

By fundamental counting principal our final answer is $\frac{(a-b)!(a-b+1)!}{(a-2b+1)!}$.


Proof by RedFireTruck