Life-size Missing Parts of 9

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SWBAT find the missing parts of 9 through subtraction.

Big Idea

I want them to develop fluency in subtraction and get them ready for future standards like 1.NBT.C.6, double digit subtraction. This can be done by providing them multiple opportunities to problem solve.

Rev Them Up

5 minutes

I love the animations and activities that this site provides: More Starfall.  Please click here and then select the numbers category.  This activity is a great fast way for my kids to get a chance to count and giggle for a few minutes.

Whole Group Interaction

20 minutes

I am hoping this lesson supports my students who continue to struggle with number sense. I want to provide them with a structure that helps them see the connection between the numbers. My goal is to provide them a model that will help them reason abstractly and quantitatively and continue to build strong math practices - and have fun while they engage in this activity! (MP2). 

There are things to prep for this lesson.  First, you need about a ten foot length of butcher paper.  The color doesn't matter, I will use white because it is what we have the most of.  Using a yard stick I will draw a life-size ten frame onto the paper.  Each box will be about a 20" by 20" square for students to be able to stand in. Check the resource section for a picture of the ten frame.

Next, I will create a dozen red circles and a dozen yellow circles. You can make them as large as you want to. These circles will be attached using tape to each of the students' chests.  Each student will either be red or a yellow counter. Check the resource section for a picture of the kids with their counters on and standing on the ten frame. 

My plan is to use a life size ten frame and place students on it to find parts of 9.  Students will wear large dots; yellow or red.  We will record what we find on a large class poster to show missing parts of 9. They will be very excited, and everyone will want their turn. I have my students assigned a class number and their number is written on Popsicle sticks. I will be drawing a sticks from the cup and if I catch them out of position or talking to their neighbor, they will be skipped.

I want them to focus on counting up to add. (1.OA.C.5).  This is a skill we have been using daily, but I have not emphasized it enough.  This is an abstract skill that has to be introduced as a concrete method at first.  I want my kids to internalize the skill of counting up to add to build their fluency in addition computation. This skill will also help my first graders transition to seeing the relationship between addition and subtraction to learn that subtraction can be used to find an unknown addend. (1.OA.B.4). The inverse relationship between addition and subtraction is very important for students to internalize.

First, I will select 3 kids with yellow dots to stand on the ten frame.  I have been teaching my students to fill up the top line first and from left to right. We will count the three students and I will ask them what number did I start with, 9.  We will count on by adding 6 kids with red dots.  We will start with 3 and count up from there as each new red dot student steps into the frame.  I will repeat we had 9 to start with and saw 3 yellow, how many was missing?  Check the resources to see an example video of how we found one missing part of 9. I will have them count how many red are on the frame, answer is 6.  I will write 9-6=3.

I will do this again four more times and find the missing parts for:

  • 9-1=8
  • 9-5=4
  • 9-2=7
  • 9-0=9

Independent Practice

15 minutes

Students will pick one number (6, 7, 8, or 9) and make their own poster showing every missing part for that number.

My students have shown me they understand they are building subtraction problems and take away means some quantity is being removed. (1.OA.C.6).

So, today I want to open it up to them to show me what they have learned and provide them a choice in what number they would like to find the missing parts of. Check the resource section for an example of completed work.


5 minutes

I call on 3 to 5 students to share their posters and explain how they were able to find all the missing parts of the numbers they chose.

I am starting to guide students towards using precise math vocabulary when they explain their thinking. 1st graders need a lot of support in developing the ability to express themselves precisely, so starting early in the year will help set the expectation that we use accurate vocabulary, complete sentences, and clear communication to convey ourselves in math throughout the year (MP6).