Yale University
Yale New Haven Teachers Institute: Solving Problems "By the Hundreds"
The Yale-New Haven Teachers Institute site contains various math exercises relating to percentage and consumer-related problems. An explanation of sales tax, a related problem and answer are given.
Council for Economic Education
Econ Ed Link: Forecasting Economics
Can you learn economics from the weather? Students will be able to integrate science, math, and economics through this engaging instructional activity. The forecast predicts some percentage chance of success.