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Relative and Absolute Thinking. The Chocolatey Cake Debate. I love chocolate, so I’m going to get a slice of the 6-layer cake!. I want the one that has more chocolate flavor, so I’m getting the 3-layer cake!.
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The Chocolatey Cake Debate I love chocolate, so I’m going to get a slice of the 6-layer cake! I want the one that has more chocolate flavor, so I’m getting the 3-layer cake! If you wanted to buy a slice of the cake that had the most chocolate flavor, which slice of cake would you buy?
Chocolatey Cake? • Work on your own to decide which cake is more chocolatey • Put your paper aside when you are done so that we know that you have finished • Then work with your group members to decide on an answer • Are you tempted to change your answer that you wrote down?
Mr. Short and Mr. Tall When Mr. Short is measured in paper clips, he is 6 paper clips tall. When he is measured in buttons, he is 4 buttons tall. Mr. Short has a friend named Mr. Tall. When Mr. Tall is measured in buttons, he is 6 buttons tall. How many paper clips tall is Mr. Tall?
How many paper clips? • Work on your own to decide the height of Mr. Tall in paper clips • Put your paper aside when you are done so that we know that you have finished • Then work with your group members to decide on an answer • Are you tempted to change your answer that you wrote down?
Proportional Reasoning • Proportional Thinkers understand that (Van de Walle): • There is a clear difference between proportional relationships and non-proportional relationships, especially in the real world • There are a variety of strategies for solving proportions or comparing ratios (that are not prescribed algorithms) • There are relationships where 2 quantities vary together (covariation)
Proportional Reasoning • It is important to develop proportional reasoning both in ourselves and our students • Develop slowly over middle school years, not just a couple weeks in 6th grade • Common Core addresses this
6.RP3 • Use ratio and rate reasoning to solve real-world and mathematical problems, e.g., by reasoning about tables of equivalent ratios, tape diagrams, double number line diagrams, or equations.
7.RP2 and 7.RP3 • Recognize and represent proportional relationships between quantities. • Decide whether two quantities are in a proportional relationship, e.g., by testing for equivalent ratios in a table or graphing on a coordinate plane and observing whether the graph is a straight line through the origin. • Use proportional relationships to solve multistep ratio and percent problems.
8.EE5 • Graph proportional relationships, interpreting the unit rate as the slope of the graph. Compare two different proportional relationships represented in different ways.
Proportional Reasoning • Activities for developing proportional reasoning (Van de Walle): • Identifying multiplicative situations • Equivalent-Ratio • Comparing Ratios • Scaling with Ratio Tables • Construction and Measurement • What type of activities are “Chocolatey Cake” and “Mr. Short and Mr. Tall”?
Relative and Absolute Thinking • What are you doing or can you do to distinguish the difference?