This article explores three attributes of teachers’ understanding of fraction magnitude: the accuracy and reasonableness of teachers’ estimations in response to fraction arithmetic tasks as well as the alignment of the estimation strategies they used with the concept of fraction magnitude. The data were collected from a national sample of mathematics teachers in grades 3–7 in which fraction concepts were taught (N = 603). The results indicated the teachers’ estimations were only partially accurate and reasonable, particularly when fraction division was involved. Furthermore, teachers’ credentials and the grade level at which they taught mathematics were significantly related to teachers’ understanding of fraction magnitude.

本文探讨了教师对分数幅度的理解的三个属性：教师对分数算术任务的估计的准确性和合理性，以及他们所采用的估计策略与分数幅度概念的一致性。数据是从3-7年级的全国数学教师样本中收集的，其中教授分数概念（N  = 603）。结果表明，教师的估计仅是部分准确和合理的，尤其是当涉及分数除法时。此外，教师的资历和他们教授数学的年级水平与教师对分数幅度的理解也有很大关系。