The ability to compute mentally. that is. to calculate exact numerical answers without the aid of any calculating or recording device, varies tremendously among indi vidual s. A quick survey of any elementary or secondary school classroom will document that some students perform mental computation quickly and accurately, whereas others are greatly hampered on even simple arithmetic problems by the withdrawal of paper and pencil. Occasionally history reports a case of an individual who ha developed extraordinary kill in mental computation. These individuals have both fascinated us and made us curious about the development of such skill. One such example wa Zerah Colburn. Born in Vermont in 1804, the son of a farmer, by the age of eight he was touring America and England displaying his exceptional mental calculating ability. He was able to give instantly the product of any two four-digit numbers. Asked to raise 8 to the sixteenth power, he gave the correct answer of 281 474 976 710 656 in a few seconds without the aid of any recording device (Eves 1969).
Barbara Reys has an interest in mathematics education at all levels.