## Tuesday, January 20, 2009

### DCM201 Multiplication of Large Numbers

Multiplication of large numbers begin in Primary 3 with multiplication of a 2 digit or 3-digit number and a 1-digit number followed by that of a 4-digit number and a 1-digit number. Later, students learn how to multiply a 2-digit number with another 2-digit number. The last two are often taught in Primary 4.

Khai taught 3D x 1D. I am pleased that he used the base ten blocks to model the process of 231 x 3 as representing 231 as 200, 30 and 1. Later he modelled the multiplication process of the hundreds, tens and ones. It is satisfying to see part of Bruner's Theory in action. One way this lesson could be improved, I told Khai, is to separates cases that requires renaming (365 x 5) from those that do not (231 x 3) and teach them in separate lessons.

In another lesson of 4D x 1D, I was excited when I saw the teacher teaching children how to use 123 x 2 to do 2123 x 2. The simplicity of it was beautiful - the new lesson simplify requires Primary 4 students to do the multiplication of the thousands (2000 x 2) and add this to 123 x 2 (which was done the year before already). It would have been great if this was done for the entire lesson. In this lesson it was done too briefly for it to have much impact on children learning. A good example of Teach Less Learn More (students learn to make connections by linking 123 x 2 to 2123 x 2).

In the third lesson, Lawrence did an excellent job applying Bruner's Theory in linking concrete, pictorial and abstract representations of 2D x 2D. You got to be there to appreciate fully what I said but breaking 34 x 42 into 4 x 42 and 30 x 42 using the area model would help children develop visualization as they learn the algorithm.

It was a good session. All the three demonstrates the basic competencies of competent teachers. They were the first three, so you can understand the nerves. It was good to see how the rest of the students who acted as students and as observers in a 'pseudo' lesson study supported their colleagues. I look forward to 27 more lessons that will unfold in the next few weeks preceeding the practicum.

#### 1 comment:

1. Hi,

I recently developed a simple educational Android game with the objective to improve my children’s math multiplication skill. After having fun with it for quite some time among families and close friends, I’ve decided to share the app it in the Google Play so that everybody can download and use it free.

I named this app XDash. The game is very simple. Players will be given 20 multiplication questions, and need to be answered correctly and as quickly as possible. The total time taken will be recorded and viewable in the top XDash Weekly and the All-Time charts.

A 12 years old in my local community (Selangor, Malaysia) managed to record 22.5 seconds which is quite impressive. Given that this application is now published worldwide, I hope that many children can easily beat that record.

The app is available at https://play.google.com/store/apps/details?id=org.ridinglinux.xdash Feel free to download try this app. If you think that this app can gives benefit to others, please rate it and share it to your friends. I accept comments and suggestions via the app’s Facebook Page at https://www.facebook.com/XDashApp .

Thank you.