We present an algorithm for a matrix-based Enigma-type encoder based on a variation of the Hill Cipher as an application of 2 × 2 matrices. In particular, students will use vector addition and 2 × 2 matrix multiplication by column vectors to simulate a matrix version of the German Enigma Encoding Machine as a basic example of cryptography. The…

To become scientifically literate, students need to interpret science concepts using numbers, text, and visuals (Lemke 2004). Scientists use multiple modes to communicate their ideas to each other and the public, including images, text, mathematical notations, symbols, diagrams, charts, and graphs. Several of the science and engineering practices…

The importance of mathematical concept development and language is recognized early in children's schooling as they mature through shape and counting experiences. The reader may recall instances of a youngster referring to a "corner" of a shape before the reader has the language of vertex. This language precision needs to continue to…

The purpose of this study was to examine the cognitive predictors of calculations and number line estimation with whole numbers and fractions. At-risk 4th-grade students (N = 139) were assessed on 6 domain-general abilities (i.e., working memory, processing speed, concept formation, language, attentive behavior, and nonverbal reasoning) and…

We present an empirical study that investigated seventh-, ninth-, and eleventh-grade students' understanding of the infinity of numbers in an interval. The participants (n = 549) were asked how many (i.e., a finite or infinite number of numbers) and what type of numbers (i.e., decimals, fractions, or any type) lie between two rational numbers. The…

This paper describes a design research study with ten second-grade students who are part of the Measure Up (MU) research and development project underway at the University of Hawai'i. Students were asked how they counted in multiple bases, specifically how they knew when to go to a new place value and why it was necessary to do so. All ten…

Presents experimental findings that indicate that some number capacity is present in 22-week old infants, long before the onset of verbal counting. Suggests that verbal counting may have precursors present during infancy. (CS)

Based on a theory of rational numbers which sees the rational numbers construct of a person as potentially built on a number of subconstructs, this study explored the view of rational numbers as operators. Significant changes in performance level and quality appeared between ages 11 and 12 and 12 and 13. (JC)

A solid understanding of equivalent fractions is considered a steppingstone towards a better understanding of operations with fractions. In this article, 55 rural Australian students' conceptions of equivalent fractions are presented. Data collected included students' responses to a short written test and follow-up interviews with three students…

This study was designed to test the effects of a sequence of 12 lessons on the ability of kindergarten and first-grade children to recognize and conserve numerousness. Two pretests were administered to the children in each grade level, the Lorge-Thorndike Intelligence Test (nonverbal) and a test of numerousness. One post-test, the test of…

Starting from the concept of one-to-one correspondence, an introduction to the different types of infinities is presented. The usual problems concerning the infiniteness of the rational numbers, the real numbers, and the unit interval are given. Several other theorems follow. (LS)

Several researchers have noted how children's whole number schemes can interfere with their efforts to learn fractions. An Australian study found that children who were successful with the solution of rational number tasks exhibited greater whole number knowledge and more flexible solution strategies. Behr and Post (1988) indicated that children…

The article considers various learning disabilities in mathematics and suggests teaching approaches such as ways to increase instructional time and the importance of building both computation skills and concepts. (DB)