Illuminations: How Many More?
Illuminations (National Council of Teachers of Mathematics)

Students write subtraction problems, model them with sets of fish-shaped crackers, and communicate their findings in words and pictures.

Illuminations: Taking Away Sets
Illuminations (National Council of Teachers of Mathematics)

This lesson encourages students to explore another model for subtraction, the familiar set model.

Illuminations: What's the Difference?
Illuminations (National Council of Teachers of Mathematics)

During this lesson, students use reasoning to find differences from numbers up to 10, using real and virtual calculators and an addition chart as tools.