Yale University
Solving Problems by the Hundreds
This site contains a study of percentage and its applications in the study of consumer related problems. Problems involving sales tax are included. Examples, explanation, solutions and a bibliography are also included in the site.
Yale University
Yale New Haven Teachers Institute: Commission
This site from Yale University provides a description of commission with example problems. Additional topics can be found on the same page.
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.