Thank you for your interest in NCTM’s Illuminations. Beginning in mid-April, all Illuminations content will be moving to nctm.org/illuminations. Interactives will remain openly available and NCTM members will have access to all Illuminations lessons with new filtering and search options. We hope you will continue to utilize and enjoy these resources on nctm.org.

## Search Results

### What Balances?

Pre-K-2
This lesson encourages students to explore another meaning of subtraction, the balance. They use subtraction facts to generate related addition facts and explore at the concrete level the idea of subtraction as the inverse of addition.

### Who's in the Fact Family?

Pre-K-2
In this lesson, the exploration of the relation of addition to subtraction is continued as the students use problem-solving skills to find fact families, including those in which one addend is zero or in which the addends are alike.

### What's the Difference?

Pre-K-2
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. They also play a concentration game.

Pre-K-2

This lesson captures students’ interests, provides an introduction to and practice with the measurable attributes of length, and assesses student knowledge. This experience focuses student’s attention on the attributes of length and gives students the opportunity to develop knowledge of and skills in using nonstandard units of measurement.

The lesson begins with a connection to children's literature. As students practice measuring length, the do so using nonstandard units.

### The Length of My Feet

Pre-K-2
This lesson focuses students’ attention on the attributes of length and develops their knowledge of and skill in using nonstandard units of measurement. It provides practice with and remediation of the measurable attributes of length.

### The Area of Things ...

Pre-K-2
Students have opportunities to recognize and use the attributes of length and area using non-standard units.

### Grouchy Lessons of Time

Pre-K-2
This lesson provides an introduction to and practice with the concept of time. The activities focus students’ attention on the attributes of time and enables students at varying levels to develop knowledge and skills in using time.

### Drop by Drop

Pre-K-2
In this lesson, students recognize and use the attributes of volume. They engage in activities that promote understanding of how to measure volume using standard units.

### The Weight of Things

Pre-K-2
This lesson introduces and provides practice with the measurable attributes of weight. It also gives an opportunity to assess student knowledge of and skill in using measurement of mass. This learning experience focuses students’ attention on the attributes of weight using hands-on activities and active learning.

### Two-Square Repeating Patterns

Pre-K-2
In this activity, students analyze how repeating patterns are generated. Using the interactive computer applet, students create, compare, and contrast pattern units of two squares and predict how patterns with different colors will appear when repeated in a grid and check their predictions.