tdg leadership seminar 2009 1 pivotal problems: knowing when to use them pivotal solutions: knowing...

TDG Leadership Seminar 2009 1

Pivotal Problems: Knowing When to Use Them

Pivotal Solutions: Knowing When to Reveal Them

George W. [email protected]

Professor EmeritusUniversity of North Carolina at Greensboro


Introductions

• What grades do you teach?

• Where do you teach?

• What is your experience in delivering professional development for teachers?

• What is something others might not know about you?


Rating Personal Understanding

On a scale of 1 (low) to 10 (high), rate yourself in terms of:

• how much you know about proportional reasoning

• how confident you are about helping students learn about proportional reasoning

• how confident you are about helping teachers learn about proportional reasoning


Goals for the Session

Solve proportional reasoning problems and explore their solutions

Identify why some problems and some solutions might be “pivotal” in helping learners understand proportional reasoning

Reflect on when pivotal problems and pivotal solutions might be most effectively presented


Pivotal Problems and Pivotal Solutions

What does pivotal mean?

When might a problem be pivotal in developing understanding?

When might a solution to a problem be pivotal in developing understanding?


National Mathematics Advisory Panel

• The Final Report of the National Mathematics Advisory Panel recommends that understanding of fractions is one of the Critical Foundations of Algebra.

• Their definition of “fractions” includes ratios and proportions, so they really are recommending “proportional reasoning” as a critical foundation of algebra.


The “3/5’s Problem”

What do you see?

Thompson, P. W. (2002). 3/5s problem. In B. Litwiller (Ed.). Making sense of fractions, ratios, and proportions: 2002 yearbook(pp. 103-104). Reston, VA: National Council of Teachers of Mathematics.


Reorganizing Thinking

What were the greatest challenges for you in the questions about the diagram?

How did the questions encourage you to reorganize your thinking about fractions and operations on fractions?


Is this pivotal?

When might this problem be pivotal?

What might you want learners to understand before the problem is posed?

What would you want learners to understand after solving this problem?


Equal or Equivalent?

Are 1/3 and 2/6 equal fractions or equivalent fractions or both or neither?

Does it matter what language we use?

How might the language we use influence what students learn?


Fractions In Between, Part 1

Find three fractions between 4/7 and 5/7.



4.5 is halfway between 4 and 5.

Is 4.5/7 halfway between 4/7 and 5/7?

Why or why not?



Find three fractions equally spaced between a/b and (a+1)/b.

Would you ask students to solve the general case?



Find three fractions equally spaced between a/b and (a+N)/b.

Would you ask students to solve the even more general case?


Is this pivotal?

When might this problem be pivotal?

What would this problem help learners learn that more traditional problems might not help them learn?



Does the same strategy work for this problem?

Find three fractions between 5/7 and 5/6.



6.5 is halfway between 7 and 6.

Is 5/6.5 between 5/7 and 5/6?

If so, is it halfway between 5/7 and 5/6?

Why or why not?



Find three fractions equally spaced between a/(b+1) and a/b.

Would you ask students to solve the general case?



Find three fractions equally spaced between a/(b+N) and a/b.

Would you ask students to solve the even more general case?


Is this pivotal?

Could this problem be a pivotal problem?

What grade level would this problem be most appropriate for?

What mathematics does this highlight that other kinds of problems might not highlight?


What is the Point?

What big mathematics ideas are embedded in these “in between” problems?

How might the solutions to these problems help move learners’ thinking forward?


What is the label?

True or false: 6 ÷ 2 = 3.3 what?

True or false: 6 ÷ 3 = 2.2 what?

Why are the labels different for the quotients?


What is the label?

True or false: 6 ÷ 2/3 = 99 what?

Is it important for students to understand what label is attached to a quotient?

Is this a pivotal idea?


Reversibility

Asking learners to “reverse” their thinking helps them create connections among ideas.

Suppose a rectangular prism has a volume of 40 cm3 and height of 5 cm.

What else can you tell me about the rectangular prism?


Thinking Differently about Familiar Ideas

Imagine what an inch looks like.

Imagine what a centimeter looks like.

What is the area of a rectangle that is

5 inches long and 3 centimeters wide?


Changing Views

How might understanding of a familiar idea change by solving a problem that presents the idea in an unfamiliar way?

How might you decide when to pose such unfamiliar problems?


Seeing the Big Picture

Solve this problem:

If 2(x - 3) = 8, then what is the value of

(x - 3)2 + 5(x - 3) - 2?

How flexible is your thinking?

Can you see the “big picture” in a problem or do you focus on the details?


Interference

For any linear measurement,

let Y = number of yards for that measurement,

let F = number of feet for that measurement.

Write an equation showing the relationship of these two variables.


Variables

How did these problems expand your understanding of variable?

Why is it important for learners to understand what a variable is?


Numbers with a Simple Relationship

Melissa bought 0.43 of a pound of wheat flour for which she paid $0.86.

How many pounds of flour could she buy for one dollar?

Post, T. R., Harel, G., Behr, M., & Lesh, R. (1991). Intermediate teachers’ knowledge of rational number concepts. In E. Fennema, T. P. Carpenter, & S. J. Lamon (Eds.), Integration research on teaching and learning mathematics (pp. 177-198). Ithaca, NY: SUNY Press.


Numbers with a Not-so-simple Relationship

Melissa bought 0.46 of a pound of wheat flour for which she paid $0.86.

How many pounds of flour could she buy for one dollar?


Reflection on Problem 1 modified

Which problem was more difficult, the “simple” problem or the “not-so-simple” problem?

What made that problem difficult?

How does the choice of numbers in a problem affect the way you (or students) might think about the problem?


Is this pivotal?

Could these problems be pivotal?

What would you want learners to take away from engagement with these problems?


A Different Kind of “Adult” Problem

In an adult condominium complex, 2/3 of the men are married to 3/5 of the women.

What part of the residents are married?

Lester, F. (2002). Condo problem. In B. Litwiller (Ed.). Making sense of fractions, ratios, and proportions: 2002 yearbook (pp. 191-192). Reston, VA: National Council of Teachers of Mathematics.


Identifying Difficulties

Why do people struggle with this problem? What makes it difficult?

How do the different solutions reveal different aspects of the underlying mathematics ideas?


Is this pivotal?

Could this problem be pivotal?

Could the solutions be pivotal?

What mathematics might this problem or the solutions to this problem help learners internalize?


Graphs

How are the two graphs below alike?

How are they different?

distance

time time

speed


Graphing Speed

Joe walks down a straight path and then turns around a walks back to the starting point.

The graph below displays how far away he was from the starting point.

Sketch the graph of his walking speed(s).

distance

time


Graphing Speed

Joe walks down a straight path and then turns around a walks back to the starting point.

The graph below displays how far away he was from the starting point.

Sketch the graph of his walking velocities. (How is this graph different from the previous graph?)

distance

time


Connecting to the Real World

Speed and velocity are complex ideas. It takes considerable time and experience to understand them fully.

When might you use these problems? For what purpose?

How might discussion of the solutions help students understand mathematics more deeply?

Is this problem pivotal?


Rating Personal Understanding (reprise)

On a scale of 1 (low) to 10 (high), rate yourself in terms of:

• how much you know about proportional reasoning

• how confident you are about helping students learn about proportional reasoning

• how confident you are about helping teachers learn about proportional reasoning

tdg leadership seminar 2009 1 pivotal problems: knowing when to use them pivotal solutions: knowing...

Documents

tdg leadership seminar

proportional reasoning

pivotal problems

pivotal solutions

greensboro slide

equal fractions

equivalent fractions

pivotal mean