Class Reflection (Realistic Mathematics in grade 7)

Standard

Linier equation system is second subjects that IMPOME students discussed in Prof. Zulkardi class. Each students is given two projects which had been done by Junior High School students grade 7 in SMP 1 Palembang, and Their solution should be analyzed and made summery. The problems are how to obtain cost if two systems are know.

The firstproblem is in figure 1.

PICT0083

Figure 1

The cost two glasses and one calculator are Rp 50,000.00, and one glasses and three calculators are Rp 50,000.00.

The Questions are :

1. Without calculating cost each item, Which one is more expensive?            Explain your reason

2. How many calculator can be bought by Rp 50,000,00? Why?

3. How much of a glasses? Give a reason.

Solution :

Almost all students can answer that question, and their solutions are different among one students and others.

This is one of their solution.

1. Glasses is more expensive than calculator because cost of a glasses            equal cost two calculators. That conclusion is made depend on figure      1.

2. One glasses and three calculators are Rp 50,000,00. Because cost of      a glasses equal cost two calculators, two calculators and three                    calculators are Rp 50,000,-. Someone can buy 5 calculators.

3. Cost of a glasses is Rp 20,000,- because cost of a glasses equal cost         two calculators.

The second problem is in figure 2.

PICT0082

Figure 2

The cost two umbrellas and one hat are Rp 80,000.00, and one umbrella and two hats are Rp 76,000.00.

The Questions are :

1. Which one is more expensive, a umbrella or a hat? Why?

2. How much of three umbrellas? How much of three hats? Explain your      reason.

3. How much of a umbrella and a hat? Give a reason.

Solution :

This is one of their solution.

1. Umbrella is more expensive than hat because buying two umbrellas      and one hat is more expensive than one umbrella and two hats.                  Differences price is Rp 4,000,00.

2. If Umbrella in the second equation change to hat in the first                         equation, Students get new equations cost of three umbrellas equal           Rp 84,000,00 and cost of three hats equal Rp 72,000,00.

3. Cost of a umbrella is Rp 28,000,00 because cost of three umbrellas         equal Rp 84,000,00, and it is divided three. Cost of a hat is Rp                    24,000,00 because cost of three hats equal Rp 72,000,00, and it is        also divided three.

Students usually use context to find solution of linier equation system. They can answer it by thinking logic and looking figure. They do not theory about linier equation system, but they answer a problem what they know in the figure.

About Zetra

Zetra Hainul Putra (1985) grew up in the small city in Pariaman-West Sumatera, Indonesia. He studied in Public Elementary School 01 Kabun Cimpago (1991 – 1997), Public Junior High School 05 Pariaman (1997 – 2000), and Public Senior High School 02 Pariaman (2000 – 2003). Then, he enrolled in a program of Mathematics at mathematics Department, Mathematics and Science Faculty at Riau University. He graduated in 2007 and became a Mathematician. After that, he worked in Moslem Junior High School As-Shofa Pekanbaru and also an assistant lecturer in Rab University Riau, Indonesia. He taught Number theory, Statistics, Linear Algebra and Mathematic logic until 2009. Finally, He received a scholarship to continued his study, Master degree on Mathematics Education, at Sriwijaya University collaboration with Utrecht University unti 2011 about Realistic Mathematics. Since 2013, he worked at University of Riau.

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