## Missing addends: finding a missing part for kids

I began by discussing the issue of my students’ easy access to action pieces (their fingers). Then I expanded on that and moved on to problems that they could solve abstractly with imagery if they needed to use manipulatives. (MP2.) This will have them thinking critically and making connections before we start our lesson. Interaction in the Whole Community Time limit: 10 minutes To introduce the idea of an unknown addend, I’ll use a story issue. The following problem and discussion points will be used by me.
Sara is the subject of our inquiry; we don’t know what she gave him, so we’ll call it x. I’ll write the equation x+6=10; we’re looking for a number that, when multiplied by 6, equals 10. We’ll replace the x with the correct number once we’ve found the answer. Then we’ll see if what we learned supports the number sentence.
I’ll bind 10 unifix cubes and split off 6 to see what’s left; the answer is 4. I’ll clarify to my students that we’ll be subtracting to find out what’s being introduced. Since I am aware that this idea is very abstract, I am using this concrete approach with cubes to introduce it to my students. There are a variety of methods for solving an unknown addition equation, but I’m going to start with the concrete approach in order to clarify, teach, and hopefully reach all of my students. OA.D.8 (1.OA.D.8) Several of my students have the higher-order reasoning skills to solve for uncertain whole numbers in an equation using counting up and/or math truth fluency. However, by incorporating this idea with a specific relation, all of my students would be able to see the correlation between using an x for the unknown. The abstract thinking process of searching for the unknown is something that First Graders are working towards (MP2). They must learn to choose methods that will aid them in reasoning quantitatively. Please see the image in the resource section for an outstanding example of one student counting up and another student solving with her cube tower. I’ll work on two more issues with my class, both of which are close to the one above.