This interactive Flash game helps students practice counting, subitizing, and grouping by 10s, as they transport Okta the Octopus and his friends to a safe ocean. The goal is to select given numbers of Oktas as quickly as possible before the timer runs out. Then users count the total number of Oktas "saved" and identify that number on a number line. Students choose from three levels of difficulty, which vary according to time limit, range of target numbers, and whether visual target cues appear. These settings are customizable. Users who count incorrectly are given the option of visual help in recounting.

This mobile app (available for both iOS and Android devices) was developed by the National Council of Teachers of Mathematics with funding from Verizon Foundation. The app is based on the Decimal Maze from the popular lesson "Too Big or Too Small". The goal is to help Okta reach the target (maximum, minimum, or a specific value) by choosing a path from the top of the maze to the bottom — adding, subtracting, multiplying and dividing as the player goes. Seven levels with seven puzzles in each level test the player's skills with operation with powers of ten, negative numbers, fractions, decimals, and exponents.

This instructional guide (PDF) is for the mobile app Pick-a-Path (both iOS and Android platforms). The guide provides professional development by discussing the math in each level of the game, giving suggestions for classroom use, and recommending related resources from Illuminations. The Pick-a-Path app is cataloged separately and listed as a related resource.

In this online version of the popular card game, students combine five given number cards, using the four arithmetic operations (addition, subtraction, multiplication, division), to arrive at a target number. This version uses the numbers 1–10 only. Users may ask for a hint or view a possible solution, although there are often multiple solutions.

This activity will help students to connect the numeral (symbol) to the number (quantity in a set).

In this Illuminations lesson, students apply their knowledge of addition equations to investigate the equivalence of two numeric expressions using the "Pan Balance-Numbers" applet (cataloged separately). An instructional plan, questions for the students, assessment options, extensions, and teacher reflections are given for the lesson as well as links to the applet and a student activity sheet(word format).

The aim of this lesson is to help students learn the process of subtracting integers through a real world discovery activity. By the end of the lesson students should be able to:
Discover a rule for subtraction integersApply the rule they discover to subtract integers with like signsApply the rule they discover to subtract integers with different signs
Students use double sided chips to manipulate "cold cubes" and "hot cubes" in order to solve the "Chefs Amazing Soup" problem. Students are asked to add and/or remove "cold cubes" and "hot cubes" to adjust the temperature of the soup and discover rules for subtracting integers in the process.

The four games that can be played with this applet help to develop counting and addition skills using frames of 10.

Thinking about numbers using frames of 10 can be a helpful way to learn basic number facts. The four games that can be played with this applet help to develop counting and addition skills. (This applet works well when used in conjunction with the Five Frame applet.)

The brief video clips on this webpage illustrate the range of number sense exhibited by students in grades Pre K-2. In interviews, Cena and Jonathan, both age 7, and Rudy, age 9, demonstrate different levels of understanding number and place value concepts. The page includes discussion questions for each set of videos as well as concluding reflection questions.

The activities in this Illumination lesson plan deal with patterns and the importance of looking at an object/item from more than a single perspective and reaffirms to learners that numerous reasonable solutions are possible. Students investigate a series of items (a list of class names and a parade of animals) that appear to be ordered in some "obvious" ways and also explore ways of sorting items ( a deck of cards and numbered horses) into two disjoint groups on the basis of some definable characteristic. Activity sheets are included in pdf format.