In an interview setting, 21 6th‐graders from four public schools in south Taiwan were asked a series of questions, related to whole and decimal numbers, designed to assess their number sense. Eight students were randomly selected from both low and middle performance levels, and five were selected from a high‐performance level, according to their mathematical capabilities. Results indicated that, regardless of performance level, very few number sense strategies (e.g. using benchmarks, estimation or numbers of magnitude) were used. The evidence also revealed that Taiwanese students tended to apply rule‐based methods and standard written algorithms to explain their reasoning. Their inclination to use paper‐and‐pencil procedures narrowed their thinking and reasoning powers: this heavy reliance on written algorithms seemed to be a major impediment to the development of number sense.

The main purpose of this study was to investigate the number sense performance of 3rd‐graders in Taiwan, and to diagnose areas of weakness or deficiency in number sense development. A total of 808 3rd‐graders participated in this study. The results indicated that these students did not perform well on each of the five number sense components (correct rates approx. 34%), and they appeared worst on the performance of “Judging the reasonableness of computational results”. Boys and girls did not show any appreciable difference in their ability to solve number sense problems. The importance of number sense should be highlighted both by teachers and in textbooks and more time and opportunity provided for students to work on this type of exercise at lower grade levels. This would require that “drill and practice” exercises in mathematics should not indeed be over‐ taught, and the teaching of number sense to children should begin as early as possible.