I begin this lesson by having the students to think about addition facts fluency.
Why is it important to know your addition math facts? What does it mean, to add?
Students have a brief time to turn and talk about what it means to add.
How is adding different from counting? How is it the same?
If necessary, I guide students to think about addition as joining and to visualize (make a picture in their heads) of what they know about how to write addition sentences.
Have the students pick up 4 of their cubes. Ask the students to add zero cubes to their cube train. Most often the students don’t do anything. Then I say, “I asked you to add zero cubes, how come you didn’t do anything?”
Why didn’t anyone add any cubes to their train? Then, I ask the students if they could write a number sentence for what we just did (4 + 0 = 4). I choose my words carefully here to refrain from asking students to write an addition sentence. I want students to get into the habit of thinking about and determining the operation, and not relying on the teacher to provide them with the operation.
Next, I have the students pick up 5 of their cubes. I tell the students that adding zero was an easy one, now it’s going to get REALLY challenging! I instruct them to add one cube to their train. When they are done, students are told to hold them up, pretending they are the Statue of Liberty. This is a strategy I use a great deal, with manipulative and individual white boards, as it tells me what students know and can do, but keeps up the pace of the lesson.
Then I ask them if they could write a number sentence to show what they just did (5 + 1 = 6), and when ready, to show their boards.
Finally, I end with the most challenging problem. Students show 3 cubes in a train and are asked to add 2 cubes to that train. Students show, and then write the number sentence (3 + 2 = 5).
Now that the idea of what we are doing today has been introduced, I ask my students to turn and talk about how this strategy of adding 0, 1, and 2 could help them build their math fact fluency.
I'm listening, but if necessary I guide students through questions to how adding 1 is just like counting, and adding 2 is just like skip counting by twos. When they are recalling number facts and building fluency, relying on what they already know is a strategy in determining the sum of an addition problem.
Students work in partners to complete the Try It Together game. In this activity, children solve both addition number sentences with 0, 1, and 2, and determine the missing addend in an addition number sentence. The students use number tiles and a bag to compete the activities.
During this lesson I noticed that when most students were practicing simply adding 0, 1, and 2 they were successful. However, when I asked them to think about problems with missing addends many struggled to determine the correct addend.
I found that it would be helpful to have the students use two color counters to build each number sentence. I would have them build the sum with one color counter. Then I would have them flip over the counter to show the first addend. I would then ask them how that model could show them what the other addend would be. It may be necessary to guide them by asking question, such as: What counters show the sum? (All of them) What counters show the addend we know? (The ones I flipped over), So how can we find out our other addend? (Look at the counters we didn't flip over).
When I was walking around monitoring their progress, I had to guide many student conversations about why they chose the addend. This was the most meaningful part of the lesson to me because students often have difficulty at this point in the year explaining their thinking. It is my hope that with more practice students will be able to explain their thinking more successfully.
Have students come back together as a class. Encourage students to turn and talk about what they learned adding 0, 1 and 2.
How could this be a useful strategy? When would you use it?
Have students share their responses with the class, using mathematical vocabulary and complete sentences. This practice is critical to the development of mathematical thinking, and can be supported with sentence frames, such as, "I know that the _______________ (missing addend, sum) is ___________ because ______________ (I counted on my fingers, I know that x is 1 more than y, etc.).