1. Multiplicative Thinking…Not Just a Topic but a Way of Thinking!*
Ted Coe, Ph.D.
Grand Canyon University
Scott Adamson, Ph.D.
Chanldler-Gilbert Communcity College
*That probably won’t kill you.

2. Multiplicative Thinking
Previously, emphasis has been on ways of DOING
Today, we will emphasize developing ways of THINKING
These ways of thinking lead to HABITS of THINKING
This will lead to effective, efficient, flexible, and fluent ways of DOING
Scott

3. Multiplicative Thinking
A unifying theme…
Proportional reasoning
Fractions
Linear functions
Exponential functions
Geometry
Trigonometry
Beyond…
Scott

4. Broomsticks Activity You have three broomsticks:
The RED broomstick is 3 feet long
The YELLOW broomstick is 4 feet long
The GREEN broomstick is 6 feet long
Ted

5. Broomsticks Activity
How much longer is the green broomstick than the red?
Additive: 3 feet longer
Multiplicative: 2 times longer
(increase of 100%)
Ted

6. Broomsticks Activity
How much longer is the yellow broomstick than the red?
Additive: 1 foot longer
Multiplicative: 4/3 times longer
(increase of ~33%)
Ted

7. Multiplicative or Additive?
Scott

8. Common Core Standards Scott
LEARNING TRAJECTORIES IN MATHEMATICS: A Foundation for Standards, Curriculum, Assessment, and Instruction, pp48-49.

9. Common Core Standards Sequencing: Scott
LEARNING TRAJECTORIES IN MATHEMATICS: A Foundation for Standards, Curriculum, Assessment, and Instruction, pp48-49.

10. Measurement What do we mean when we talk about “measurement”? 08/13/09
1010
08/13/09
Measurement
What do we mean when we talk about “measurement”?
Ted

11. Measurement
“Technically, a measurement is a number that indicates a comparison between the attribute of an object being measured and the same attribute of a given unit of measure.”
Van de Walle (2001)
But what does he mean by “comparison”?
Ted

12. Measurement Determine the attribute you want to measure
Find something else with the same attribute. Use it as the measuring unit.
Compare the two: multiplicatively.
Ted

13. Measurement
Ted
From Fractions and Multiplicative Reasoning, Thompson and Saldanha, (pdf p. 22)

15. What Does it Mean to be Steep?
Discuss at your table and come up with your definition of steep.
Each group will report out their definition.
Scott

16. How Could we Determine Which Stairs were steepest?
What should we measure?
Scott

17. Let’s Do it!
Each group has a tool. I’d like you to measure the height and depth of the stair using your tool.
As a group discuss what you’d like to do with those measurements.
Scott

18. Steepness Measurement
What would you like to do with your two measurements?
The steps on the stool are _____________ times as high as they are deep.
The steps on the stool are _____________ times as deep as they are high.
Which would you use as your steepness measure? Why?
Scott

19. More Examples
Scott

20. More Examples
Scott

21. Where could the classroom discussion go from here?
The steepness of a line is called slope.
When students are reasoning multiplicatively (and are aware of it), measuring the slope of a line simply becomes a multiplicative comparison. This gives meaning to “rise over run” and you’re students developed it!
Scott

22. Geometry
The circumference is about how many times as large as the diameter?
The diameter is about how many times as large as the circumference?
Ted

24. Geometry
Angles
What attribute are we measuring when we measure angles?
Ted
CCSS Grade 4 p. 31

25.
Ted

26. Geometry
Area:
TEd

27. Area of whole square is 4r^2
08/13/09
08/13/09
Area of whole square is 4r^2
Area of red square is 2r^2
Area of circle is…
Ted 27 27

28. Geometry
Similar Triangles
Ted

29. Pythagorean Theorem Pythagorean Theorem
TEd

30. Constant Rate

31. Trigonometry Right Triangle Trigonometry

32. Irrational? Irrational Numbers
The first proof of the existence of irrational numbers is usually attributed to a Pythagorean (possibly Hippasus of Metapontum),who probably discovered them while identifying sides of the pentagram.The then-current Pythagorean method would have claimed that there must be some sufficiently small, indivisible unit that could fit evenly into one of these lengths as well as the other. However, Hippasus, in the 5th century BC, was able to deduce that there was in fact no common unit of measure, and that the assertion of such an existence was in fact a contradiction. 
Ted
11/2/2012

33. Hippasus, however, was not lauded for his efforts: according to one legend, he made his discovery while out at sea,
Ted
11/2/2012

34. Hippasus, however, was not lauded for his efforts: according to one legend, he made his discovery while out at sea, and was subsequently thrown overboard by his fellow Pythagoreans
Ted
11/2/2012

35. Hippasus, however, was not lauded for his efforts: according to one legend, he made his discovery while out at sea, and was subsequently thrown overboard by his fellow Pythagoreans “…for having produced an element in the universe which denied the…doctrine that all phenomena in the universe can be reduced to whole numbers and their ratios.” 
Ted

36. “Too much math never killed anyone”
…except Hippasus
Ted

37. Archimedes died c. 212 BC during the Second Punic War, when Roman forces under General Marcus Claudius Marcellus captured the city of Syracuse after a two-year-long siege. According to the popular account given by Plutarch, Archimedes was contemplating a mathematical diagram when the city was captured. A Roman soldier commanded him to come and meet General Marcellus but he declined, saying that he had to finish working on the problem. The soldier was enraged by this, and killed Archimedes with his sword.
Ted
11/2/2012

38. Ted
The last words attributed to Archimedes are "Do not disturb my circles" 
11/2/2012

39. “Too much math never killed anyone”
…except Hippasus
…and Archimedes.
Ted

40. Exponential Functions
Which bank account grew more in one year?
Account A grew from $100 to $145.
Account B grew from $50 to $76.
Scott

41. Bank Accounts 120−95=25 what? 120 95 ≈1.26 what?
Consider a bank account that grew from $95 to $120 over THREE years.
Use an additive comparison for these two numbers. What does your answer mean?
Use a multiplicative comparison for these two numbers. What does your answer mean?
120−95=25 what?
≈1.26 what?

42. Bank Accounts 25 3 ≈8.33 what? 3 120 95 ≈1.08 what?
If the terms of growth remained constant, ($95 to $120, 3 years)
What is the annual additive growth for this account? What does your number mean?
What is the annual multiplicative growth (factor) for this account? What does your number mean?
25 3 ≈8.33 what?
≈1.08 what?

43. What’s next? Where could you go next?
What other mathematics ideas can be built upon multiplicative thinking?
Both

44. Ted Coe ted.coe@gcu.edu Scott Adamson s.adamson@cgc.edu
Questions?
Ted Coe Scott Adamson
Both