Reflection: Developing a Conceptual Understanding Using data from a table to answer comparison problems: how many more... - Section 2: Introduction to New Material


In comparison problems, students oftentimes add the two numbers instead of setting up a number sentence that reflects the problem (subtraction or creating an unknown start addition problem)

Take this problem for an example:

Jake has 10 red skittles and 4 yellow skittles.  How many more red skittles does he have?

Because there is no "action" in this problem (i.e: nothing is being taken away or added), students sometimes choose to simply add the two numbers (10 + 4). It is also useful to name these problems as comparison problems and differentiated them from problems that have "action". 

In order to avoid this particular pitfall, use cubes to demonstrate what a comparison problem is asking.  Set out 10 cubes and then line up four cubes underneath.  Ask your students: should I add these together in order to determine HOW MANY MORE?  Students will frequently be able to understand that they are comparing so they should either set up the problem like 10-4 = ______ or 4 + ________= 10.  

My students have struggled with these kinds of problems but with frequent modeling and use of visuals they have began to develop a greater conceptual understanding of what comparison problems are asking. 

  Common student mistake
  Developing a Conceptual Understanding: Common student mistake
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Using data from a table to answer comparison problems: how many more...

Unit 4: Tables
Lesson 2 of 4

Objective: SWBAT solve comparison problems using data from a table

Big Idea: Students use data from a table to solve "how many more" comparison problems. Students identify, use, and share their own strategies for solving comparison problems.

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