2013 T3 Interna-onal Conference
Steve Phelps [email protected] 1
Steve Phelps Madeira High School
Cincinna-, OH [email protected]
Nspired Probability, Polynomials and CAS 2013 T3 Interna-onal Conference
1
Goals
• Discover the connec-on between probability objects (spinners, dice) and polynomials
• Use polynomial mul-plica-on to model probability situa-ons (the sum of two spins of a spinner, or the sum of the rolls of two dice)
• Use polynomial factoring to model probability situa-ons (construc-ng new dice that meet certain condi-ons)
2
Essen-al Ques-on
Is it possible to find a different pair of six-‐sided dice with posi-ve integer face values that have the same distribu-on of rolls as a pair of standard six-‐sided dice?
3
Let’s begin to answer this Essen-al Ques-on by playing a game.
4
Spin the two spinners and add the results. What are the possible sums?
5
Possible Sums
-‐3, -‐2, -‐1, 0, 1, 2, 3, 4
6
2013 T3 Interna-onal Conference
Steve Phelps [email protected] 2
Play a Game
• Write down the 10 sums that YOU think will be the first ten sums to appear as a result of spinning the two spinners 10 -mes.
• The first person to cross off all their numbers “wins.”
• We will model the spins using a List & Spreadsheet.
7
Seang up the Spreadsheet
8
From Spinner to Polynomial
2x −1 + x 0 + x 2
• The EXPONENTS are the values on the spinner.
• The COEFFICIENTS are the rela-ve weights of each value (-‐1 occurs twice as oeen as 0 or 2),
9
x −2 + x −1 + x 1 + x 2
From Spinner to Polynomial
• The EXPONENTS are the values on the spinner.
• The COEFFICIENTS are the rela-ve weights of each value.
10
Spinning Both Spinners
11
Mul-plying the two polynomials is equivalent to spinning the two spinners
What Does it Mean?
• The EXPONENTS are the SUMS of the two spinners. • The COEFFICIENTS are the number of ways the sum can occur.
12
2013 T3 Interna-onal Conference
Steve Phelps [email protected] 3
Do It With Probabili-es!
• The EXPONENTS are the values on the spinner. • The COEFFICIENTS are the probabili-es of each value.
13
Let’s work towards an answer to our Essen-al Ques-on by exploring
a simpler problem.
14
Two Four-‐Sided Dice: What is The Distribu-on of The Sums?
15
Two Four-‐Sided Dice: What is The Distribu-on of The Sums?
One way to roll an 8, two ways to roll a 7, three ways to roll a 6, four ways to roll a 5, and so on...
16
Is it possible to construct two other 4-‐sided dice that have the same distribu-on of sums?
17
Factor
There are six factors! 18
2013 T3 Interna-onal Conference
Steve Phelps [email protected] 4
Rearrange the Factors
• Both dice are 4-‐sided • One dice has one 4, two 3’s and one 2 • The other has one 4, two 2’s and one 0
19
What About This?
• One die is 8-‐sided, the other is 2-‐sided. 20
What About This?
• Both dice are 4-‐sided • One dice has one 3, two 2s and one 1 • The other has one 5, two 3’s and one 1
21
Back to our Essen-al Ques-on
Is it possible to find a different pair of six-‐sided dice with posi-ve integer face values that have the same distribu-on of rolls as a pair of standard six-‐sided dice?
22
Rolling Two 6-‐sided Dice
Each dice is represented as a polynomial by
x + x 2 + x 3 + x 4 + x 5 + x 6
23
Factor
• There are 8 factors • We need to choose factors that will create a polynomial whose coefficients are all posi-ve and sum to 6.
24
2013 T3 Interna-onal Conference
Steve Phelps [email protected] 5
This Would NOT Work...
25
This DOES Work
26
Sicherman Dice
27
Differences
• Other than the obvious, how are Sicherman Dice different from a pair of 6-‐sided dice
Standard Sicherman
28
Extension Ques-ons for Sicherman Dice
• How would Monopoly change with these dice?
• How would Backgammon change with these dice?
• How would Craps change with these two dice? • How would Yahtzee change using these dice?
29
References
• hop://plus.maths.org/content/os/issue41/features/hobbs/index
• hop://plus.maths.org/content/non-‐transi-v-‐dice
• hop://en.wikipedia.org/wiki/Sicherman_dice • hop://mathworld.wolfram.com/SichermanDice.html
• hop://www.cut-‐the-‐knot.org/arithme-c/combinatorics/Sicherman.shtml
30