Subtraction: Using Objects

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Objective

SWBAT subtract using objects.

Big Idea

Interacting with games on the Smart Board always appeals to my students and boost their interaction. My students will practice "take away" using a website game and "hands on" using cubes.

Rev Them Up

5 minutes

I need my students to practice "take away" with me today and identify that subtraction can be some going away.(1.OA.A.1). Subtraction is a difficult concept for first graders to comprehend because it takes more abstract thought to look at a picture and tell yourself that so many are gone, yet you can still see them on the page because we just cross them out.  Subtracting using objects is important  for students to actually see items are gone from the whole amount. Subtracting using objects allows my students to reason abstractly and quantitatively while attending to precision and gaining the correct answer. (MP 2 & 6). When I introduce word problems I attempt to have factual, matching items for what the problem states, but sometimes it is not available. I always use unifix cubes to represent items in  word problems because these are the tools students will have to use all year in our room. This requires students to use abstract thought and solve quantitatively by using their imagination that substituting cubes for other items still results in correct answers.

I will pour 5 skittles in Dixie cups and prepare enough for each student to get one cup. I prepare them first thing in the morning or during my planning time, so I can make a fast delivery for our lesson time.  These little cups make serving easy, so I ask my students to place their hands on their shoulders while I deliver.  30 seconds will go by and tah-dah, delivery done.  We are ready to do some "take away" subtraction.  I will ask my students;

"Please place your skittles on your desk and count them."

I will write the problems we create on the board, so the verbal discussion will go quickly.

"Yes, we have 5, now eat 1. "How many are left? What should I write on the board for our math problem?

5-1=4

"Now eat 2 of your skittles." "How many are left? What should our subtraction problem be for our list?"

4-2=2

"Now eat 2 of your skittles." "How many are left? What should our subtraction problem be for our list?"

2-2=0

"Now were ready to play a game together. We are going to practice more "take away" today, using a math game on the Smart Board."

Group Interaction

5 minutes

I will have my students help me solve subtraction problems using some of the online math games found here.

I will open the website up on my Smart Board and begin by selecting some students to help me solve problems.  I will pick the Rabbit Runaway game format because it supplies my students an opportunity to see a whole number then take however many away that the problem calls for.  When I can see my students understand how the game is played, I will begin calling each student up one at a time to solve a problem. Look at the resource section and watch the video of my students helping me at the beginning to solve problems and learn the game. Also, you can see the starting page for the game, "Soccer Subtraction." 

If you have your own website or interactive math software to use, go for it.  The main thing you should look for in quality technology for this lesson is that it supplies your students the opportunity to take away from a whole amount, not just X it out or move it over, but that it disappears.  This will make subtraction a more concrete activity because they need to see that something is gone, which is one definition of subtraction.  Being able to solve word problems is a difficult task for First Graders because it it an abstract process. A story problem can tell them there are 7 apples and Tom ate 3, but they don't actually have the 7 apples in their hand and they do not know who Tom is. You must introduce word problems with concrete items that are factual or representative of what the problem provides.

Independent Practice and Informal Assessment

10 minutes

I want my students to continue helping me solve problems of take away.  I will provide all my students ten cubes and I will give them a problem to solve.

Jan had 7 apples and gave 3 to Johnny.  How many does she have now?  

Todd had 5 pencils and gave 2 to Sara. How many does he have now?

Rick had 9 rocks and dropped 3 on the ground. How many does he have now?

Rebecca had 7 Hot wheel cars. She gave 2 to her little brother.  How many does she have left?

I want them to use their cubes to solve the problem.  I will be walking the room and taking anecdotal notes on how my students are doing in solving their problems. A great way to take notes is to have  a sheet of sticky notes ready to go with each child's name pre-printed on them.  This way you know if you have checked on that student or not.  Simple little notes can be made, such as, got it, adding instead of subtracting, success, needed a prompt, etc. You can even go here to gain a template to pre-print your student's names on sticky notes.

I will continue providing verbal problems and observing students until I have assessed every student's progress.

Closing

5 minutes

I will ask my students to gather at our meeting carpet and begin a discussion about our math time today. I want them to share with a partner about what we did and what they learned from it. I will pair them up by ability; a low student with a high student. 

Students I want you to turn to your partner and tell them 2 things: what kind of math did you do today and what did you do to make it work. How did you solve your problems?