In this lesson, students continue to build their conceptual understanding of adding numbers within 1,000. They relate the use of place-value disks on a place-value chart to the algorithm, recording compositions as new groups below in vertical form. As they move the manipulatives, students use place-value language to express the action and physically exchange 10 ones for 1 ten and 10 tens for 1 hundred, if necessary. They record each change in the vertical form, step by step.