Two approaches are discussed for calculating the work necessary to pump water from a conical or parabolic container. The direct method derived from the definition of work is easy to misuse, as illustrated by a student's incorrect solution. (JP)

Nine examples of this principle show what a powerful tool it is. Several map coloring theorems are proven and some exercises are listed. (MP)

A computer program generates sets of simultaneous linear equations for students to solve; the program also solves the systems and provides teachers with solutions. (SD)