This is a free program taken from a CD-ROM collection of over 200 mathematics puzzles, available on the developer's Web site
. Developed by a veteran teacher, these visually-oriented puzzle games have a simple interface and are designed to provide math problems in context to middle-school (grades five through nine) students.
In this particular program, students must use mental math and proportional thinking to find common percentages of given numbers. You can view a screenshot of this program by clicking here.