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Just made a couple of videos explaining multiplication in a visual way, using the ‘Box Method’

Playlist on youtube, here


Counting with coffee Beans on grid paper

When I started teaching my son maths we did a lot of counting coffee beans.  We would arrange 12 beans in groups of 3 and groups of 4… The idea was to start building up intuition and then segway into multiplication.

Don’t ask me why coffee beans.. I must be a bad parent!  The beans just happened to be handy, being dark they were easily visible when put on 5mm math grid paper and fit nicely in the squares.  You can use small buttons or raisins even.  Its pretty tactile, so works okay for young kids [ as long as they are old enough not to swallow small things ]

Abstracting to Multiplication

Later we drew the ‘beans’ in the squares and then just drawing a circle in the box instead of placing a bean.  This gradually led to  tracing out the rectangle outlines of the groups and let the squares on paper take the place of actual beans.. so it abstracts really well in a fairly natural and unforced way.

There are some nice ‘tricks’ you can do on squared paper that grow out of this approach –

  • every rectangle is a multiplication product, so you can use it to figure out any times table question
  • you can work out all the times-tables and write them in the top right square before reciting them
  • introduce distributive property (a+b)*c = a*c + b*c by showing the rectangles add up
  • ask.. are there any numbers that cant be made by a rectangle product? [ numbers]
  • show square numbers – 1,4,9,16 …
  • you can show how to add 2n+1 to n squared to get the next square number
  • you can introduce series – 1+3+5+7+ … and show how they sum to make the square numbers
  • make a stepped-triangle 1+2+3+4+5+6 and show how two of these can be put together to make a rectangle, which leads to sum 1 to n = n(n+1)/2

So this approach leads very naturally into some really nice mathematics.  Along the way it reinforces the rote learning of times tables (auditory repetition) with visual intuition.

The web app – introducing Doctor X

I thought there was probably an App or web page to do this kind of thing interactively.  I googled around and found lots of times table grids, math systems but nothing that seemed to take the grid-paper-rectangles-and-counting-beans approach into an interactive medium.

I made notes on what the app might look like, and then spent some time making a quick prototype in Javascript.  I found It needed a way to step through some basic usage notes and examples, so I added a howto box.  Then we came up with a silly name for this thing.

Anyway, here is the current version of the visual grid calculator for kids, which I’m calling :

“The Doctor X Amazing Griddable Multiplication Contraption”

The Doctor X Amazing Griddable Multiplication Contraption

When I get time Ill make some more in-depth tutorials and worksheets on some of the concepts I mentioned above.   Let me know what you’d like to see,