Asked & Answered

The Asked & Answered department shares excerpts from discussion threads on the online MyNCTM community. In this issue, featured threads highlight responses to members' questions regarding 1st grade number sense, multiplication and division of fractions, issues of definition and precision related to circles, and the value of rationalizing denominators.

Research of composition of milk protein concentrates

Emergence of the dairy products enriched with milky proteinaceous concentrates is connected with low level of consumption of protein the population. Results of a research of structure of two samples of milk protein concentrates – Promilk 852 FBI and Promilk Kappa Optimum for the purpose of their further application in production of dairy products are presented in article. Fractions of proteins of milk protein concentrates with use of size of molecular weight are defined. As a result of electrophoretic division of fractions of proteins the method of a free electrophoresis by means of a cell for an electrophoresis of MINI-PROTEAN has received an initial electrophoregram. In the studied samples the number of fractions of serumal proteins and casein is identified. Absolute values of fractions of serumal proteins and casein in samples of milk protein concentrates are calculated. On the basis of the received values of fractions of serumal proteins and casein their percentage in milk protein concentrates is determined. The received results allow to draw a conclusion that the studied samples of milk protein concentrates can be used in production of dairy products as an additional component for increase in nutrition value of a ready-made product.

PENGARUH METODE PROBLEM SOLVING DAN MOTIVASI TERHADAP HASIL BELAJAR MATEMATIKA SISWA KELAS V SDN 04 MUARO SEI LOLO KABUPATEN PASAMAN

This research aimed to reveal the influence of problem solving method and motivation to mathematics learning outcomes in the fifth grade of elementary school on the subjects of multiplication and division of fractions. The type of this study was experimental research using quantitative method of quasi experiment. The design of the research was explained in the form of 2x2 factorial. The populations of the research were all fifth grade students of elementary school in Sub-district of Mapat Tunggul Selatan belonging to a group of high school consisted of 7 schools. The technique of sample collecting used was purposive sampling. The data of the research were obtained from questionnaire of motivation and mathematics learning outcomes. The technique of data analysis was done using two-ways ANOVA technique. The result of the analysis showed that: (1) there were differences of the learning outcomes of multiplication and division of fractions between students who were taught problem solving methods and students who were taught in a conventional way, with significance value of 0,000. (2) There were differences of the learning outcomes of multiplication and division of fractions between students who had high motivation and the learning outcomes of students who had low motivation, with significance value of 0,001. (3) There wasn’t an interaction between learning methods and students’ motivation to the students’ learning outcomes of multiplication and division of fractions, with significance value of 0,438.

A Learning Trajectory of Indonesian 12-years Old Students Understanding of Division of Fractions

The purpose of this study was to describe mathematical hands-on activities that can support students to gain better understanding of dividing fractions. This preliminary research phase was started by testing, analyzing, and refining the initial hypothetical learning trajectory (HLT), then in the pilot experimental phase the revised HLT was implemented, and ended with the teaching experimental phase by developing a learning trajectory for 12-year old students in understanding division of fractions. In developing the trajectory, a design research methodology was employed by using four contextual-based learning series (sharing biscuit, sharing remaining chocolate bar, arranging bedroom mats, and running around school yard), including providing some concrete materials or pictorial models as manipulative tools. Seven mathematics experts and twenty five 12-year old students were involved during the research. The four designed learning goals were determining the quotient of division of integer by proper fraction, proper fraction by integer, two proper fractions, and two fractions. Students succeeded in demonstrating their understanding and stated that 16:1/2 = 32; 25/36:5 = 5/36; 24/64:1/2 = 6/8; and 15/2:3/4 = 10 respectively at the end of each designed activity. The interesting results of this study are not a proof, so that a much larger study is needed to determine if the results are due to this approach or due to the teachers’ enthusiasm or what is known as the Hawthorne Effect.