Students will solve addition and subtraction word problems to 1000 using an Open Number Line as a math tool. Teachers will model how to organize an open number line as they remind students how to decompose a number using place value. Students will then use the chunks the number is broken into as they add it all back up. Many problems are provided for whole group instruction. Projecting the work on a board so the teach can model is an option. The lesson could also be used for small guided groups, independent work, partner work, Tier Intervention, and differentiation. There are blank cards included so student can write their own problems, A student response sheet is included to each child has work they are accountable for. The response sheet could be used for informal assessment or as formal assessment.