• Communications of Mathematical Education
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• v.23 no.3
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• pp.707-734
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• 2009

The purpose of the study was to investigate how children understand addition and subtraction of fractions and how their understanding influences the solutions of fractional word problems. Twenty students from 4th to 6th grades were involved in the study. Children's understanding of operations with fractions was categorized into "joining", "combine" and "computational procedures (of fraction addition)" for additions, "taking away", "comparison" and "computational procedures (of fraction subtraction)" for subtractions. Most children understood additions as combining two distinct sets and subtractions as removing a subset from a given set. In addition, whether fractions had common denominators or not did not affect how they interpret operations with fractions. Some children understood the meanings for addition and subtraction of fractions as computational procedures of each operation without associating these operations with the particular situations (e.g. joining, taking away). More children understood addition and subtraction of fractions as a computational procedure when two fractions had different denominators. In case of addition, children's semantic structure of fractional addition did not influence how they solve the word problems. Furthermore, we could not find any common features among children with the same understanding of fractional addition while solving the fractional word problems. In case of subtraction, on the other hand, most children revealed a tendency to solve the word problems based on their semantic structure of the fractional subtraction. Children with the same understanding of fractional subtraction showed some commonalities while solving word problems in comparison to solving word problems involving addition of fractions. Particularly, some children who understood the meaning for addition and subtraction of fractions as computational procedures of each operation could not successfully solve the word problems with fractions compared to other children.

• Education of Primary School Mathematics
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• v.27 no.2
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• pp.187-198
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• 2024

The addition and subtraction relationship and the multiplication and division relationship are explicitly dealt with in second and third grade mathematics textbooks. However, these relationships are not discussed anymore in the problem situations and activities in the 4th, 5th, and 6th grade mathematics textbooks. In this study, we investigate the calculation principles of subtraction and division in the elementary school mathematics textbooks. Based on our investigation, we justify the addition and subtraction relationship and the multiplication and division relationship at the level of children's understanding so that we discuss some problem situations and activities where the relationships can be applied to subtraction and division. In addition, we suggest educational implications that can be obtained from children's applying the relationships and the properties of equations to subtraction and division.

• Proceedings of the Korea Institutes of Information Security and Cryptology Conference
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• 1995.11a
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• pp.151-162
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• 1995

보다 짧은 길이의 덧셈/뺄셈 사슬($addition_{traction-chain}$)을 찾는 문제는 정수론을 기반으로 하는 많은 암호시스템들에 있어서 중요한 문제이다. 특히, RSA에서의 모듈라멱승(modular exponentiation)이나 타원 곡선(elliptic curve)에서의 곱셈 연산시간은 덧셈사슬(addition-chain) 또는 덧셈/뺄셈 사슬의 길이와 정비례한다 본 논문에서는 덧셈/뻘셈 사슬을 구하는 새로운 알고리즘을 제안하고, 그 성능을 분석하여 기존의 방법들과 비교한다. 본 논문에서 제안하는 알고리즘은 작은윈도우(small-window) 기법을 기반으로 하고, 뺄셈을사용해서 윈도우의 개수를 최적화함으로써 덧셈/뺄셈 사슬의 길이를 짧게 한다. 본 논문에서 제안하는 알고리즘은 512비트의 정수에 대해 평균길이 595.6의 덧셈/뺄셈 사슬을 찾는다.

• Journal of Educational Research in Mathematics
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• v.19 no.2
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• pp.307-319
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• 2009

Current school mathematics introduces addition/subtraction between natural numbers, fractions, decimal fractions, and square roots, step-by-step in order. It seems that, however, school mathematics focuses too much on learning the calculation method of addition/subtraction between each stages of numbers, to lead most of students to understand the coherent principle, lying in addition/subtraction algorithm between real numbers in all. This paper raises questions on this problematic approach of current school mathematics, in learning addition/subtraction. This paper intends to clarify the fact that, if we recognize addition/subtraction between numbers from the viewpoint of 'measuring' and 'common measure', as Dewey did when he argued that the psychological origin of the concept of number was measuring, then we could find some common principles of addition/subtraction operation, beyond the superficial differences among algorithms of addition/subtraction between each stages of numbers. At the end, this paper suggests the necessity of improving the methods of learning addition/subtraction in current school mathematics.

• School Mathematics
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• v.18 no.1
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• pp.175-191
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• 2016

In the elementary school mathematics textbook that has been revised in 2013, the instructional sequence for teaching addition and subtraction, which had remained unchanged for three decades since 1982, was finally changed in 2013. Particularly, the addition and subtraction of two-digit numbers without regrouping, such as 72+25=97 or 85-24=61, are taught earlier than the composing and decomposing of the number 10 using other numbers. This study examines the appropriacy and validity of these changes. However, the reason for these changes in the national curriculum or teacher's guide could not be determined. Further, several references emphasize the addition of two single-digit numbers, such as 7+8=15, and the subtraction of a single-digit number from a number between 11 and 19, such as 16-9=7, as basic facts. In other countries' textbooks, the teaching of addition and subtraction up to the number 20 is prioritized before teaching the addition and subtraction of two-digit numbers without regrouping. The results of this study indicate that these changes in the instructional sequence in the textbook that was revised in 2013 need to be reconsidered.

• Education of Primary School Mathematics
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• v.25 no.2
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• pp.197-211
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• 2022

In this study, we tried to find a way to improve the pedagogical decision-making practices related to the presentation order of 'large number' and 'small number' in problem situations of subtraction of the natural number. For this purpose, the elementary school teachers' perception about problem situations in real-life context of subtraction of natural numbers was investigated, and the collected data were analyzed qualitatively and quantitatively to identify teachers' pedagogical perceptions. As a result of this study, it was confirmed the need for consideration on how to set up a problem situations in real-life context of subtraction so that students can develop their ability to solve various types of problems. To this end, not only in a problem situation of subtraction where you have to think of 'large number' first and 'small number' later, but also about the introduction of problem situations in real-life context of subtraction in which you think about 'small number' first and 'large number' later, which often appears in real-life. You will need to recognize the need. And you should have a pedagogical view on this. The results of this study will be able to contribute to the preparation of pedagogical method that can expand the understanding of various problem situations where subtraction is applied from the lower grades of elementary school.

• School Mathematics
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• v.19 no.1
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• pp.137-151
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• 2017

This study aims to investigate the possibility of elementary students' generalization from three-digit numbers to multi-digit numbers in principles for addition and subtraction. One of main changes was the reduction of range of numbers for addition and subtraction from four-digit to three-digit. It was hypothesized that the students could generalize the principles of addition and subtraction after learning the three-digit addition and subtraction. To achieve the purpose of this study, we selected two groups as a sampling. One is called 'group 2015' who learned four-digit addition and subtraction and the other is called 'group 2016' who learned addition and subtraction only to three-digit. Because of the particularity of these subjects, this study covered two years 2015~2016. We applied our addition and subtraction test which contains ten three-digit or four-digit addition and subtraction items, respectively. We collected their results of the test and analyzed their differences using t-test. The results showed statistically meaningful difference between the mean score of the two groups only for four-digit subtraction. Based on the result, we discussed and made some didactical suggestions for teaching multi-digit addition and subtraction.

• Communications of Mathematical Education
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• v.16
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• pp.331-344
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• 2003

본 연구의 목적은 예비 초등교사의 덧셈과 뺄셈에 대한 교과 지식과 교수학적 지식이 어떠한가를 알아보는 것이었다. 29명의 예비 초등교사가 연구에 참여하였으며 자료는 개방형 답을 하는 질문지를 사용하여 수집하였다. 분석결과 예비 초등교사들은 문장제에서 의미론적 구성과 합병과 구차의 상황에 대한 이해에 어려움을 가지고 있는 것으로 나타났다. 교수학적 방법에서는 알고리즘에 의한 설명 방법을 주로 사용하였으며 뺄셈을 설명하는데 몇 가지 오개념을 보였다. 이 결과는 앞으로 초등교사양성대학의 프로그램 개발과 운영에 기초가 될 것이다.

• Education of Primary School Mathematics
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• v.19 no.3
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• pp.177-191
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• 2016

Students can calculate the addition and subtraction problem using informal knowledge before receiving the formal instruction. Recently, the value that a computation lesson focus on the understanding and developing the various strategies is highlighted by curriculum developers as well as in reports. Ideally, a educational setting and classroom culture reflected students' learning and problem solving strategies. So, this paper analyzed the similarity and difference with respect to the numeric sentence and word problem in the addition and subtraction. The subjects for the study were 100 third-grade Korean students and 68 third-grade American students. Researcher developed the questionnaire in the addition and subtraction and used it for the survey. The following results have been drawn from this study. The computational ability of Korean students was higher than that of American students in both the numeric sentence and word problem. And it was revealed the differences of the strategies which were used problem solving process. Korean students tended to use algorithms and numbers' characters and relations, but American students tended to use the drawings and algorithms with drawings.

• Communications of Mathematical Education
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• v.37 no.2
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• pp.213-231
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• 2023

The purpose of this study was to analyze and derive pedagogical implications from elementary mathematics textbooks that align with the revised 2015 curriculum. Specifically, the focus was on the chapters related to simplifying fractions, finding a common denominator, and performing addition and subtraction of Fractions with Different Denominators. The analysis revealed that the overall structure of these chapters was similar across the textbooks, but variations existed in terms of the main activities and the textbook organization. Furthermore, different textbooks employed various types and quantities of visual representations. When designing lesson directions and content, it is crucial to consider the strengths and weaknesses of each visual representation.