Illuminations: Begin With Buttons

Begin With Buttons

Shirts Full of Buttons

Students explore subtraction in the comparative mode by answering questions of “How many more?” and “How many less?” as they match sets of buttons. They also make and discuss bar graphs based on the number of buttons they are wearing.

Learning Objectives
 
Students will:
  • explore the results of comparing sets
  • review the term “difference”
  • construct and make inferences from a bar graph

Materials
 
Sticky notes
Shirts Template
Buttons
Crayons

Instructional Plan

Ask the students to count the number of buttons they are wearing, and write that number on a small sticky note. Then draw on the board the outline of a bar graph, with the vertical axis labeled in numbers up to twelve, and the horizontal axis labeled “Number of Buttons.” Label the graph “Number of Buttons We Wore Today.” Call on students to place their sticky notes in the column that shows the number of buttons they are wearing. [As they place the notes, be sure the first note in each column lies on the horizontal axis and that the bottom of each succeeding note touches the top of the last note in that column.]

 

 

When the students are ready, encourage them to pose questions that can be answered from the graph, such as how many of us had on five buttons? How many more students had on six buttons than had on three buttons today? How many fewer of us had on four buttons than had on two buttons today? Ask the students to make a copy of the graph. [It will be used in Lesson 8.]

Next display two copies of the Shirt Template and put six buttons on one shirt and four buttons on the other shirt. Ask the students how the number of buttons on the shirts could be compared. Repeat with other addend pairs. Then model a subtraction problem in which two sets are compared. For example, if Joan’s shirt has five buttons and Sue’s shirt has three buttons, how many more buttons does Joan’s shirt have? How many fewer buttons are on Sue’s shirt?

Display a large piece of chart paper where all the students can see it. Point out the columns you have labeled “Buttons on the Smiley Face Shirt,” “Buttons on the Starburst Shirt,” and “Difference.” Call on a volunteer to enter the sum, one addend, and the difference on the chart.

Next give each pair of students the template with two shirts, buttons, and a piece of paper for a work mat. Now have the students pose and answer comparison questions.

Begin by helping students model a comparison in which a set of three and a set of four are compared. [If students have difficulty comparing, have them add buttons to the shirt with less buttons until the shirts have the same number of buttons. Then suggest that the students circle the added buttons and count them.]

Next, encourage the students to make up other comparison situations using any numbers they wish. Call on students to share their problems. Finally, ask what would be recorded if both shirts had seven buttons [7, 7, 0]. Prompt the students to add other such entries.

You may wish to suggest that the students record in pictures and in equation form one of the comparing problems for their portfolios.

Questions for Students
 

Can you show how to compare the number of buttons on two shirts?

Which difference on our chart shows that one shirt had five buttons and the other had three buttons?

If you compared a shirt with seven buttons and another with seven buttons, what would be the difference?

If you compared a shirt with seven buttons and another with zero buttons, what would be the difference?

If you had a shirt with four buttons, how would you make a shirt with three more buttons? With three less buttons?

Suppose you had a shirt with five buttons. How many buttons would have to be on another shirt so that there is a difference of two? Is there another answer?

[7 and 3 are equally valid answers.]

Assessment Options
 
  1. At this stage of the unit, it is important for students to know how to:

    • model comparison subtraction using the set model
    • identify differences and addends
    • recognize the effect of subtracting all and subtracting zero
    • construct and make inferences from a bar graph
  2. The Questions for Students may assist you in understanding your students’ level of attainment of the concepts in this lesson.
  3. As you reach the final lesson in this unit, it may be useful to consider how much individual students have grown, and to use this information to plan strategies for remediation and extension activities. This would also be a good time to ask individual students to talk with you about the entries in their unit portfolios.

Teacher Reflection
 
  • Which students are able to compare sets and record the differences?
  • Which students need additional instruction and practice on the objectives of this lesson?
  • Can most of the students find the difference when one addend is zero? Can they find it when the addends are the same?
  • Which children met all the objectives of this lesson? What are appropriate next steps for them?
  • What parts of the lesson went smoothly? Which parts should I change the next time that I teach this lesson?

NCTM Standards and Expectations
 
Number & Operations Pre-K-2
  1. Use multiple models to develop initial understandings of place value and the base-ten number system.
  2. Develop a sense of whole numbers and represent and use them in flexible ways, including relating, composing, and decomposing numbers.
  3. Develop understanding of the relative position and magnitude of whole numbers and of ordinal and cardinal numbers and their connections.
  4. Count with understanding and recognize "how many" in sets of objects.
  5. Understand the effects of adding and subtracting whole numbers.
  6. Understand various meanings of addition and subtraction of whole numbers and the relationship between the two operations.
  7. Develop and use strategies for whole-number computations, with a focus on addition and subtraction.
  8. Use a variety of methods and tools to compute, including objects, mental computation, estimation, paper and pencil, and calculators.
  9. Develop fluency with basic number combinations for addition and subtraction.
This lesson prepared by Grace M. Burton.
  
1 period   

NCTM Resources

Principles and Standards for School Mathematics
National Council of Teachers of Mathematics Thinkfinity Verizon Foundation
More and Better Mathematics for All Students
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