Reflection on Paper:

Design Research on Addition and Subtraction Up to 100

Using Mental Arithmetic Strategies on an Empty Number Line

At the 2nd Grade of SDN Percontohan Komplek IKIP Jakarta

(Puspita Sari, Dede de Haan, Zulkardi, 2008)

Innumeracy problems experienced by many students nowadays might be caused by inappropriate approach in teaching algorithm in primary schools which seems to be premature and less contextual according to some experts. In order to deal with the problems, realistic approach involving mental arithmetic strategies is suggested in advance, that is, emphasising more on number values rather than number digits.

In case of teaching addition and subtraction to 2nd grade students, an empty number line – number line with no numbers on it – seems to fit the need since it could encourage students’ informal counting strategy to develop. The use of context as demanded in RME is highly required to stimulate a meaningful learning toward the students. For the research, the context applied was celebrating the 63rd Indonesian Independence Day, due to the current d-situation.

The Use of Empty Number Lines in Learning Implementation

1. Empty number line as a *model of*

In this part, the number line was introduced using a string of beads which was coloured alternately every ten beads, the length of which would be measured by students using a paper strip. This would smoothly redirect the students to think of empty number lines.

2. Empty number line as a *model for
*Here, the students were guided to work without the strings, but with the concept it applied, to solve addition and subtraction problems related to the context.

Another thing that could be developed through this manipulative was students’ sense of relationship among numbers, especially its relation to tens. This applied when students were about to place a certain number, for example, number 37 can be observed as 40-7,30+7 or 35+2. This could stimulate students’ mental arithmetic capability.

Despite its implementation in addition, empty number line can also be applied in subtraction by viewing it either as taking away or adding on.

The use of empty/ almost empty number line should be thoughtful and with appropriate context, unless, it could be a meaningless strategy.

NB:

This summary is based on my own understanding toward the reflected article. If there are mistakes on it, I beg to your pardon.

The real article could be accessed in the following link:

http://eprints.unsri.ac.id/899/1/Puspita_Sari-dede-dehan-zulkardi.pdf