I had introduced the nummer kasten in a previous post, which is used in Heguru class to teach the concept of addition and subtraction.
After a few classes, I had a better understanding of its usage, and decided to improve on my rather badly-made beta version.
Here’s the new improved box, complete with different coloured sections (red and blue), with a slotted divider in the centre to allow balls to pass from one section to the next.
It comes with a sliding cover that allows me to reveal one portion at a time:
How to use
To give a clearer explanation of how the box is to be used to explain addition/subtraction, here’s an example using 3 balls.
I start by showing G that there are 3 balls, then place the balls one by one into the red section. I then close the box and shake it so that some of the balls fall into the other compartment.
Now, I slide the cover open again, revealing that there are 2 balls left on the red side. Usually at this point, G will open his eyes in wonder. 😉 I like that there is always the element of surprise, since we will not know how many balls to expect when the box is opened.
I will ask G to count the number of balls left in the red compartment, and where the remaining ball is. He has done this a few times to know that there is a separate compartment. I then ask how many balls there should be on the other side, then slide open to reveal the answer. 🙂
I find that the nummer kasten complements the dot bar, where the same concept is taught using blue and red dots on a 3×3 grid. The same equation is represented here:
This is one of the many interesting ways that the maths concept is presented in Heguru class, and I find that it brings the subject to life. I wish I had known of this method when I was teaching C, I wouldn’t have had such grief!
How do you teach maths?