Hit the Target with Subtraction Number Sentences

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SWBAT create subtraction sentences within ten, both verbally and in written form.

Big Idea

Target math provides them the opportunity to have fun while creating subtraction number sentences. They will play a great subtraction game and then recreate their actions in written form.

Rev Them Up

15 minutes

There are two main pieces to prepare for this lesson and you have a choice in how you handle it; you can have the kids do it with you and give them counting and following directions practice, you can prepare ahead of time, or you can ask a parent to help.

The first thing is to prepare their math tool; a bead stick. The bead stick is made from a pipe cleaner. You can cut it in half like I did, or you can use the entire 12" length of the stick.  The kids will need 10 beads threaded onto the bead stick.  I curled one end of the stick up to make sure the beads stayed on, then I threaded the beads onto the stick and curled the other end up.  I purposely selected beads that did not slip on too easy because I wanted them to have to move them one at a time and not shove a bunch all at once when they are working.  

Many of my students are still developing good number sense and I did not want to confuse them in solving take away, with beads that are slipping side to side. 1.OA.A.1 wants our students to solve take away using objects and my less experienced students can do this with me planning ahead and building in support. I want them to build fluency in solving subtraction problems and the bead sticks with repeated practice will fulfill this goal.

Subtraction seems to be more abstract to little ones than adding.  They can picture having some and getting more easier, than having some and part of them disappear.  My students who do not have a strong one-to-one correspondence yet, literally need objects to see and touch and move. 

The students can definitely help you create these, but I was under time restraints, so I prepped over the weekend and will have them ready to go. Check the resource section to see the bead sticks.

I will have the kids check them for me to see if I gave them all ten beads and practice sliding them one-at-a time across their stick. Look at the picture of their excited faces showing off their math tool. These will remind you of an abacus, which is exactly where I got the idea from.

Next, you need to prepare their targets.  Look at the targets on the sidewalk in the resources.  Look at the close-up pictures for you to see I made each one of them different.  I went outside before school started to an area that I knew no one would be walking or would get wet during the day and drew the targets with sidewalk chalk.  They are about six feet in diameter and I only used numbers ten or less.

You will also need a bean bag or some type of item to toss on the target, for each group you plan to use.  I divided my class into four groups and used four bean bags.

Whole Group Interaction

20 minutes

It's nice to take advantage of the wonderful fall weather and get them outside to do something different for math.  This lesson also provides them with a tool to help with the accuracy of their answers by counting bead sticks (MP5).

Your students will be playing target subtraction.  They will use a bean bag to toss at the number and use their bead sticks to solve their problem.  It will be subtraction using numbers to 10.  Every bead stick has ten beads. Whatever number their bag lands on has to be subtracted from ten and then they must tell me their subtraction sentence, ex. 10-4=6.  

Try watching Target Math Explanation for an explanation as we began the game.  I will divide my students into groups and sit in front of their targets.  I will tell them to stay on the grass and off the concrete. This gives them enough distance to toss their bags.  One selected student will stand up and I will walk her through the steps of the game and everyone else can watch.  Watch the video taped explanation in the resources. This helped her use her math tool appropriately and built precision into the problem-solving. (MP5). Showing my students an example of how to play their game will help my visual and auditory learners understand what to do.  

After that I will have every student stand in the front of the line and take their turn.  They can tell the person behind them their math problem and solve it, then that second person can check their answer with their bead stick before the first person can go to the end of the line. After each student tells their math sentence, they will hand the bag to the next person and go to the end of the line and the game continues. This will be a great way for them to build fluency in subtraction and the foundation knowledge to decompose ten. (1.OA.C.6). Also, having the students check each others work will force them to critique the reasoning of others (MP3).

It is very important to have them state their problem verbally before going to the back of the line because it catches misunderstandings.  If you do not have them telling what they found or understand, you will not know if they are comprehending or even playing the game correctly.  Check out Scaffolding for a Student to see how I support a student who made a mistake on 10-10=0.

Independent Practice

10 minutes

After we finish our target math game outside we will come back into the classroom and recreate some of the subtraction number sentences we discovered. 

I will supply students with 3 copies of the bead problem sheet  They must create six subtraction problems pertaining to our target math. I will draw a target on the chalkboard for them to pretend with and select numbers from and create their math sentences. You could have your students use their bead sticks to solve their number sentences or their fingers.  I am going to have them use their fingers since that is a tool they will always have on them.

After I pass the worksheets out and draw the target, I will ask my students what number did every one of our problems start with outside? Ten is the number I want them to remember.  We have spent our last few lessons finding the missing parts of 6, 7 ,8, and 9.  I want this lesson to not only provide them practice in writing number sentences, but to see how numbers are connected together within the number ten.  Watch the video in the resources of a student developing a bead number sentence.

The previous subtraction lessons have begun showing my students there is a connection between addition and subtraction and there are several strategies to solve subtraction problems, 1.OA.6.  I have had students solve 7-4=3, by knowing that 3+4=7. I had a student solve 8-1=7 by telling me he could start at 1 and count up to 8 and find his answer for the difference.  They are truly applying their growing number sense and having fun in the process.


5 minutes

I ask 3 to 5 students to share out one of their number sentences and articulate the strategy they used (counting back, beads, drawing, using the addition fact, etc.) to solve the number sentence.