This SMART Notebook lesson has been adapted from Eureka Math 3rd grade Module 2 Lesson 20, estimating differences. I have included the majority of the lesson and adapted it to fit the needs of my students. Included is an essential question,teacher instruction slides, problem set, and exit ticket. Even if you are not using Eureka Math in your classroom, this lesson still can be used because it correlates to the Common Core for 3rd grade.