Bugs in the House Subtraction

Review of Bugs in the House Subtraction lesson from Bridges

Mathematical Trajectory: This is an important lesson in First Grade because it is the introduction to Subtraction. 

Math Goal:  It is possible to solve for the change unknown, start unknown, and end unknown using manipulative,( Use appropriate tools strategically), and you don't always have to subtract, take away, when subtracting.

Relevant Stands:  1:OA.A.1, 1:OA.B.4, and most importantly: 1:OA.D.8

• CCSS.Math.Content.1.OA.D.8 Determine the unknown whole number in an addition or subtraction equation relating three whole numbers. For example, determine the unknown number that makes the equation true in each of the equations 8 + ? = 11, 5 = _ – 3, 6 + 6 = _.

Sociomathematical Norms:  The posters for Mathematical Habits of Mind and Interaction will be referenced and pointed out through out the lesson. In order to make sense of the problem students will be asked to use Private Reasoning Time, they will have to Explain how they are Thinking, they will need to Listen to Understand, they will be asked and will be asking Genuine Questions, they will explore Multiple Pathways, they will Compare and contrast Logic and Ideas, they will Critique and Debate each other, ( Construct viable arguments and critique others reasoning), and Math will be the Final Authority. 
I plan to focus on students making connections between other mathematical ideas such as addition.  I will also emphasize metacognition because I anticipate  mistakes and stuck points.  This will also include some disequilibrium.  (Make sense of problems and persevere in solving them.)  (Reason abstractly and quantitatively)   


Justification/Generalization:  For answer unknown I can take the minuend and split it into 2 groups to get the difference :   5 - 3 = ___.  (Attend to precision)

I can add the subtrahend to the difference to  get the minuend .  ___ - 3= 2 

Prior Knowledge: In Number Corner we have played around with addition and subtraction in the games we have played.  (We have not taught subtraction explicitly until now.)

Metacognition:  Since I am expecting mistakes and stuck points I plan to select and sequence students to share their work at the document camera.  ( Model with mathematics) I anticipate students having a difficult time getting started so I will first show the work of a student that has started.  I plan to show multiple ways the students are making sense of the problem. (Make sense of problems and persevere in solving them.)  Eventually, I plan to construct a public record for each problem solved.

Instructional Focus: 
1c. Metacognition and reflection about their reasoning, conclusions, mistakes, disequilibrium, and developing understandings?

2d.  Working with Public Records of student thinking  to focus attention on mathematical ideas and questions that are important to highlight  as context for sense making and /or to record for reference later.  (Look for and make use of structure) and ( Look for and express regularity in repeated reasoning)

Evidence: As I observe the students working and selecting  and sequencing  their work at the document camera I will be able to see who has it and who does not.  I should be able to tell from their drawings if they have the concept of subtracting. I will also look for the students who can do multiple representations using pictures and number sentences.

Exit Task:  As an Exit Task I will have 3 problems. 

 __ - 1 = 4
5 - __ = 2
8 - 4 = __

 want to see how many get the unknown problems and how many get the basic  problem of 8 - 4 = __.  I will be curious to see if any use addition to get the subtraction problem. I want to see if they can use manipulitives to solve the problems.  I want to see if they can make any connections to the problems.  I want to see who struggled and got it and who still needs more play time with the bugs.