Addition and subtraction are incredibly important concepts for third graders. However even though students have been learning about addition and subtraction since kindergarten, this always seems to give students trouble. I feel that part of students’ trouble is the fact that they don’t understand the concepts of addition and subtraction. They memorize key words and algorithms without true understanding, and in return we see the same errors again and again.
I’ve been working on my Third Grade Addition and Subtraction Unit, so that I can teach conceptually AND not spend too long on this unit. While I absolutely recognize its importance, I also know that it is easy to get “stuck” in this unit and run out of time of your other important math concepts. Hopefully this blog post will give you a few ideas on teaching addition and subtraction! If you’re looking for more advanced lessons, be sure to check out this blog post.
Addition and Subtraction Facts
Before I get into the nitty gritty of how I teach addition and subtraction, I would like to share what I don’t focus on-addition and subtraction facts. Yes! I want my students to know their addition and subtraction facts, but I simply don’t have time to devote my classroom instruction to theses. Instead, I focus on my third grade content, and the vast majority of my math fact practice will be with multiplication facts. My hope is that through skills practice and number talks, my students will become more fluent with their addition and subtraction facts. Fortunately, the majority of my students do come to me knowing their addition and subtraction facts. They may not all be extremely fast, but they are efficient. However, I usually have one or two students who have an extremely difficult time with addition and subtraction facts. I teach these students to draw a number line on the bottom of their paper, and they have to use the number line during our third grade level addition and subtraction tasks. This is such a simple, yet effective, accommodation for students. They don’t redraw the number line for every problem, but reuse the same number line for all of their work. Students can become very fast with a number line, and it helps build confidence with students.
I like to begin the unit with a brief addition and subtraction pretest. This gives a quick overview of where I need to begin the unit. Naturally, students are all over the place with their results, but it’s good information for developing math groups. I give my pretest about a week before I start my actual addition and subtraction unit, because I use that extra time to preteach my students who struggled the most. This helps make my grade level addition and subtraction lessons more meaningful to those students.
Addition and Subtraction Unit
My Addition and Subtraction Unit consists of 15 lessons and activities. I do teach this unit differently than I teach any of my other math units, but it’s been a very effective strategy for me.
I begin each lesson with a whole group mini lesson. During students’ work time, students have a task that they complete, while I meet with students in need extra help in a small group. I determine my small groups based on the addition and subtraction pretest, and I use the data from my small groups to determine the following day’s small group. For instance, if on Monday I met with a group who needed to work on 2-digit plus 2-digit problems, and by the end of math I only had two students who still needed extra practice, I would begin working with those two students on Tuesday. Once they grasped the concept, I would move to all students who need help with 3-digit plus 3-digit problems.
My first week of mini lessons in the unit focus on addition strategies for larger numbers. I teach friendly numbers, doubles, place value, adding up, and the algorithm. Naturally, I don’t expect my students to fully grasp each strategy, but I use them as a general overview for my lessons to come. I want students to at least be familiar with the terms.
My second week of mini lessons in the unit focus on subtraction strategies for larger numbers. I teach adding up, removal, friendly numbers, keeping a constant difference, and the algorithm. Once again, I don’t expect students to fully grasp everything I teach, but I do want them to have a familiarity with the terms. We will be using the terms for the next several weeks in our number talks, which is where my students will develop a more thorough understanding. Since the focus of my number talks are all strategies other than the algorithm, I use my small group time for teaching the algorithm.
I tried really hard to create fun and innovative ways to practice addition and subtraction in my students’ work time. There was an emphasis on word problems, especially two-step word problems, because this is always what gives students the most trouble. You’ll find activities for the properties of addition and finding the missing number in addition and subtraction number sentences.
I do like to have a collection of resources for my students around the classroom. I like to display an addition and subtraction anchor chart for the algorithm, as well as provide examples in students interactive notebooks. Rather than using a traditional math interactive notebook, I use My Math Reference Notes, because they save me SO MUCH time cutting, folding, and pasting.