Prior to this grade, students used various strategies and representations to solve problems involving addition and subtraction of multi-digit numbers (first within 100, and then within 1,000).

This lesson enables the teacher to see the strategies and representations that students use, which may include base-ten blocks or diagrams, number lines, or equations. It also elicits what students know about using place value to add or subtract (for instance, combining hundreds and hundreds, tens and tens, and ones and ones). The work here prepares students to learn algorithms for addition and subtraction, which also are grounded in the same ideas.

What strategies did you anticipate that your students would use today? Which did you not anticipate?