**Introduction**

The observation was executed in the IGM School, Palembang, and the teacher is Mrs. Mefi in collaboration with Ms. Saliza and Ms. Nila, whom both are International Master Program on Mathematics Education (IMPoME) students of the year 2010. Mrs. Mefi has joined the PMRI workshop in conducted at the Sriwijaya University, Palembang, for a week last three months. She teaches in the beginning phase for third grade students. The topic taught was about “comparing numbers from 500 to 999”.

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**Observation Question:**

“How do the students compare numbers from 500 to 999?”

**Description **

The students worked in groups consisting of 4-5 students. Mrs. Mefi, the teacher, started with giving the “My Snack” context that she bought for distributing to each group. She asked the students about their snacks and also asked the students to write down the prices of their snacks, and divide it into 3 parts, in hundreds, in tens, and in units. She continues with explaining on how to compare prices on the whiteboard in front of the class.

. Three students, Ina, Gina, and Suriana, wrote their snack price, divide the prices into 3 parts, and compared prices between each other on the whiteboard. Ina said that her snack price was “seven hundred and fifty”, and then she wrote “7” for hundreds, “5” for tens, and “0” for units. Gina follows by saying that her snack price was “six hundred and seventy five”, and then she wrote “6” for hundreds, “7” for tens, and “5” for units. Suriana continues Gina by saying that her snack price was “eight hundred”, and then she wrote “8” for hundreds, “0” for tens, and “0” for units. Ina tried to compare her snack price to Gina’s snack price and said that her snack price is higher than Gina’s snack price, but is lower than Suriana’s snack price. However, Suriana said that she didn’t know why her snack price is bigger than Ina’s snack price. Mrs. Mefi asked other students to help Suriana. Diana, Suriana’s friend, explained that “800” has “8” for hundreds and “750” has “7” for hundreds and we know that “8” is bigger than “7”, so that’s why Suriana’s snack price is higher than Ina’s snack price. She continued by asking other students and they give different opinions. Some agreed with Diana but some disagreed. Some students said that “eight hundred” should be lower than “seven hundred and fifty” because the “800” value is 8 (8+0+0) while the “750” value is 12 (7+5+0). “Eight” is smaller than “twelve”. This showed that some students already understand about comparing numbers, while some other not. Mrs. Mefi tried to understand the students’ explanations, but she didn’t give public judgement on whose answers were the right one.

She asked the students which is the bigger one between “500” and “600”, and all answered “six hundred”. For simple numbers as such (in hundreds) they can easily compare the numbers, but they were confused when they were given complex numbers like “581” and “601” and then to compare them between each other. To make the students fully understand, Mrs. Mefi played with “number tower” in which some sticks and some “Styrofoams” contain 3 parts of numbers, the largest size for hundreds, medium size for tens, and the smallest size for units. Each group got 2 number towers which contain 3 sticks and 9 styrofoams and 2 pieces of paper. She asked the students to compare all numbers from worksheet using the numbers towers given for each groups, and then their friends from another group have to give comments about their work. Every group likes very much to discuss with another group. At the end of the class, Mrs. Mefi asked the students to collect their group work.

**Conclusion**

The students were confused when they faced the complex numbers compared with the simple numbers like “eight hundred” and “seven hundred and fifty” because these numbers have a lot of difference in their symbols. It has a relation with their understanding of the concept of comparison of place values. Teachers have to support the students by giving some additional concrete activities which can help the students in learning about place values comparison.

**Documentation**

The Result of Student Worksheet (left), Two Number Towers (top right), and Student Presentation (bottom right)

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