We will begin the week by re-capping adding integers using the two-color chip model. It will also include writing equations for real-world examples involving addition of negative and positive numbers. We will then move on to modeling integer subtraction using the chips. We will start by understanding that for every expression that includes subtraction, we can write an equivalent expression using addition of the opposite of the number being subtracted. A conceptual challenge students may encounter is not being able to extend their thinking to subtracting negative numbers. It can be very confusing that the result of a difference may be larger than the number they start with. This work helps students deepen their understanding of operations, because they explore and use a relationship between addition and subtraction. Students learn the new connection of these operations that subtracting gives the same result as adding an opposite, and that it is often more efficient to think about a subtraction.
I have been teaching 7th grade Mathematics for 10 years. I have worked at two IB MYP schools, one in Houston, Texas, and at West End Middle for 8 years. Please feel free to email me if you have any questions, comments or concerns.