This short video and interactive assessment activity is designed to teach third graders about classifying all types of triangles by lengths of sides.

Students learn about gear ratios and power by operating toy mechanical cranes of differing gear ratios. They attempt to pick up objects with various masses to witness how much power must be applied to the system to oppose the force of gravity. They learn about the concept of gear ratio and practice calculating gear ratios on worksheets, discovering that smaller gear ratios are best for picking objects up quickly, and larger gear ratios make it easier to lift heavy objects.

Investigate collisions on an air hockey table. Set up your own experiments: vary the number of discs, masses and initial conditions. Is momentum conserved? Is kinetic energy conserved? Vary the elasticity and see what happens.

This short video and interactive assessment activity is designed to teach second graders about using a place value chart to compare and write decimal inequalities.

This short video and interactive assessment activity is designed to teach second graders an overview of comparing decimals.

This short video and interactive assessment activity is designed to teach third graders about comparing numbers using greater than and less than.

Watch your solution change color as you mix chemicals with water. Then check molarity with the concentration meter. What are all the ways you can change the concentration of your solution? Switch solutes to compare different chemicals and find out how concentrated you can go before you hit saturation!

This is a mathematical number sense puzzle designed for partners to work through.

This Nrich problem is intentionally difficult as it stands, but this allows us to focus on promoting resilience and perseverance with children.

In this engineering, math, and sustainability project students answer the question, “Can I ride 53 miles on a bike from the energy of a single burrito?” They must define their variables, collect and analyze their data, and present their results. By the end of this project, developed by Allen Distinguished Educator Mike Wierusz, students should have all the information they need to design a burrito that would provide them with the exact caloric content necessary to ride 53 miles.

This short video and interactive assessment activity is designed to teach second graders about decomposing decimals into place values up to hundredths.

In this first part of a two-part lab activity, students use triple balance beams and graduated cylinders to take measurements and calculate the densities of several common, irregularly shaped objects with the purpose to resolve confusion about mass and density. After this activity, conduct the associated Density Column Lab - Part 2 activity before presenting the associated Density & Miscibility lesson for discussion about concepts that explain what students have observed.

Concluding a two-part lab activity, students use triple balance beams and graduated cylinders to take measurements and calculate densities of several household liquids and compare them to the densities of irregularly shaped objects (as determined in Part 1). Then they create density columns with the three liquids and four solid items to test their calculations and predictions of the different densities. Once their density columns are complete, students determine the effect of adding detergent to the columns. After this activity, present the associated Density & Miscibility lesson for a discussion about why the column layers do not mix.

This short video and interactive assessment activity is designed to teach third graders about determining unknown angles in parallelograms.

'Tricks' tap into children's natural curiosity and can provide the motivation for exploring the underlying mathematics in order to unpick how they are done. This Nrich problem explores a "trick" to provide an engaging context in which to explore place value and in particular 'adding nine' as 'adding ten and subtracting one'.

In this YouCubed task. students examine what happens when you keep continuing a pattern, forever. Students delve into the infinite and find the patterns and their area.

How many calories are in your favorite foods? How much exercise would you have to do to burn off these calories? What is the relationship between calories and weight? Explore these issues by choosing diet and exercise and keeping an eye on your weight.

This lesson unit is intended to help teachers assess how well students can: Understand the concepts of length and area; use the concept of area in proving why two areas are or are not equal; and construct their own examples and counterexamples to help justify or refute conjectures.

Students will examine how human actions and population changes can affect the environment. Students will examine a series of photographs that compare famous landmarks (Times Square, the Saltair Pavilion in Utah, Laguna Beach, and Niagara Falls) across time, and then they will identify human-generated changes in the physical environment, such as the addition of bridges and roads. Students will also examine U.S. Census Bureau population and housing data to see how population changes can contribute to changes in the physical environment. In addition, students will describe the impact of these changes on the environment.

This short video and interactive assessment activity is designed to teach second graders an overview - tenths.