Selecting Tools for Addition

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Objective

SWBAT select appropriate strategies for solving addition problems.

Big Idea

Problem solving can be made easier when tools are used strategically.

Introduction & Expectations

15 minutes

One thing you did a lot of in 2nd grade was addition and subtraction. We are going to build on that in 3rd grade by learning ways that will help us more quickly solve problems. There are a lot of math tools that we can use that can make it easier for us to picture our numbers. Some problems are easier to solve when I use blocks, some are easier with dinosaurs and others are best with only my pencil and paper!

I want to set the expectation for students that the work they produce is something they need to be proud of and should show all of their hard work. I also want to model how we use math tools appropriately within the classroom.

I am going to use these foam dice and roll them twice. I rolled a 2...and a 7. I need 3 volunteers to help me solve this problem using some of the tools we have in front of us.

I have students select manipulatives from a variety of classroom objects (counters, dice, base 10 blocks, unifix cubes, plastic dinosaurs etc) and solve the problem. We discuss as a group which tools made it easier or harder to solve (MP5). Key questions: What if the number was 200 and 700? Would you use plastic dinosaurs to solve the problem if it was 435 and 327? Why is it important to look at the problem before we choose which tool you will use to solve?

I roll the dice again, this time creating 2-digit by 2-digit numbers, and again ask students to come choose manipulatives to help me solve. I will write a sentence explaining why we used the tools we did for solving the problem and expect students to do the same. 

My two goals for this lesson are to develop and build a strong classroom culture for learning and to set and model clear expectations around mathematical practices.

Culture - a mathematical classroom is a place where we respect our shared journey, learning to persevere when confronting complexity (MP1), to listen to ourselves (learn who we are as mathematical thinkers), as well as others (MP3). We always, always, always, explain our thinking. 

Language / tools - in order to represent mathematics we learn a new language and how to use it. We also become increasingly familiar with tools - and the ways to use them.

Practice

30 minutes

Today I want you to think about the tools you have around you in our room and which ones will make problem solving easier for you. We are only adding for today, and you can roll your dice to create 1, 2 or 3 digit numbers. Remember, when your numbers get bigger, the tools you need to solve might change, too! Your work will be displayed for all of the other students and teachers to see, so make sure that it shows all of your hard work and excellence. Make sure you write a sentence for each problem telling others which tools you used to solve and why you chose them.

The first week is important for students to get used to my routines and procedures in math and to start thinking about how to solve problems on their own. Most importantly, it is important for me to show students that they will be making decisions this year in math, they will be doing the heavy lifting and problem solving, and they will have to defend the choices they make. While students are working I am leaning in with students to ask them questions about their work and their choices and making anecdotal notes (noting who excels at addition, who works well independently, who struggles to find a way to solve their problems etc) to better inform my instruction moving forward and to better understand my students as math thinkers.