# Circumstance of Geometry Planes

Classroom Observation in SD Muhammadiyah 1 (Second Report)

The second classroom observation in SD Muhammadiyah I was done in May 27, 2010. In this observation I and my friend observed the third grade that was taught by Mrs Rosmaini, namely IIIC class. In that time, she taught about Circumstance of Geometry Planes through approaches of PMRI. She used ice cream sticks as her media to explain the circumstances of geometry planes. When the first time Mrs Rosmaini introduced media that she used, the students seemed enthusiasm to follow the lesson. The students had been familiar with ice cream stick because those days they like to play using it. They bought it with price around Rp 1,000 for five sticks. Then, they usually used ice cream sticks to make some objects or anything that they like.

The first activitiy, the students were divided in seven groups which each group consists of four students. Each group got fifty ice cream sticks. By using it, the students were asked to make at least three geometry planes. Here are some results of the students’ activity in making geometry planes using ice cream sticks.

After the students made some geometry planes, they were asked to draw what they made using ice cream sticks in a paper. Then, they had to determine what the name of each geometry plane was, and how many sticks they need to make it. Here are some of their drawings according to geometry planes that they made by ice cream sticks.

From this activity, students could know the name of each geometry plan they made and could determine how many stick they need to make it. Then, they could easily understand that the number of sticks to make a geometry plan showed the circumstance of that plan.

The second activity, Mrs Rosmaini gave a matter to her students like bellow:

Mrs Rosmaini explained to her students that she had fifty sticks, then she want to make 2 houses in two different shapes. From here, the students were asked to make houses using sticks that they had. She also explained that the houses had to contain shapes of geometry planes. Here are some the results of students’ activity in this session:

As in the first activity, in this second activity the students were asked to draw it in a paper.  Then, they determined how many sticks they need to build their house. Here are some drawings of houses that they had made:

From this activity, the students could determine some geometry planes from a house and they could determine circumstances of each of geometry plane in that house. However, in this activity they still had difficulty to determine the whole circumstances of their houses. They considered that all sticks that they used to make a house showed the circumstance of that house. Hence, after this activity Mrs Rosmaini explained that the circumstance of their house could be determined just by counting sticks in the border of their house. Finally, most of students could understand it. They looked happy during the class was going on. Some of them also interested to determine about geometry planes of their real home.

Before Mrs Rosmaini finished her lesson, she had asked the students to look at the result of other groups’ activities. This made them could compare their results, and they could get better understanding about shapes of geometry planes and how to determine their circumstances.