The vision to transform mathematics classrooms into learning communities in which students engage in mathematical discourse is a remarkable hallmark of the current movement, led by the National Council of Teachers of Mathematics, to reform mathematics education (NCTM 1991, 2000). According to NCTM, “the discourse of a classroom—the ways of representing, thinking, talking, agreeing and disagreeing—is central to what students learn about mathematics as a domain of human inquiry with characteristic ways of knowing” (NCTM 1991, p. 34). Indeed, both the Principles and Standards for School Mathematics (2000) and Professional Standards for Teaching Mathematics (1991) recommend that teachers of mathematics provide opportunities for children of all ages to participate in mathematical discourse.
The four-function calculator is widely used by students and teachers in elementary schools. Although other types of calculators are available, the number of choices has been limited up to now. Recently, however, calculator manufacturers, including Casio (fx-991Wplus, fx-115Wplus, and fx-300Wplus), Sharp (EL-520RB and EL-506RB), and Texas Instruments (TI-30X IIS, TI-34 IIX, and TI-15), have introduced two-line calculators, and more are being developed. These calculators can display an expression on one line and the computed result on the second line. These calculators offer a variety of features in addition to the two-line display, but this article focuses on the development of numbers and operations using the TI-15, which is specifically designed for use in elementary school and middle school classrooms.
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