Mental computation and estimation are topics we keep hearing about. Although mental computation is not a stranger to the history of mathematics education, estimation is a relative newcomer to the curriculum. The history of mental computation dates back to when arithmetic was first taught. Historically, it was emphasized bccause of its social utility—shopkeepers needed to “cipher” total of grocery bills quickly. The current emphasis on both mental computation and estimation has a different origin. As teachers, we want students to take advantage of whatever computatonal tool is most appropriate for the situation at hand. Yet unless students have developed the skill both to compute mentally and to estimate and the awareness to take advantage or whichever is appropriate, we will not see it happen.
Barbara J. Reys has an insrest in mathematics education at all levels.