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.

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.

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.

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