PBS
Pbs: Balancing Scales to Solve Equations
Predict the number of blocks you need to equal the weight of one bag and then test your theory. This interactive exercise focuses on using critical thinking skills to add and subtract items on the scales to achieve balance and visual...
National Council of Teachers of Mathematics
Nctm: Illuminations: Pan Balance Numbers
Use this tool to strengthen understanding and computation of numerical expressions and equality using a balance scale.
University of Texas
Inside Mathematics: Boxes [Pdf]
This task challenges students to demonstrate an understand of the concept of equality using scales and balance beams.
University of California
Uc Davis Geo Wiki: Chemical Budgets of Oceanic Elements
To the extent that the composition of the ocean remains constant, the rate at which any one element is introduced into seawater must equal the rate of its removal. A listing of the various routes of addition and removal, together with...