Why do this problem
is based on one of many ways of supporting
multiplication. The examples consider numbers from 6 to 9 but does
the method work, or can it be modified to work for other numbers?
The focus is on the why, rather than any sense that this is a
preferable way of calculation. But this is an interesting
representation nevertheless and leads to the question, "What sort
of person could have thought of this for the first time?".
Rather than show the images on the site it might be good to take a
small number of learners in the group into your confidence and ask
them to show examples and give the answers without explanation,
asking the rest of the group to make sense of the code.
Once the code has been cracked the question has to be asked why it
works. This may be something you wish to leave learners to think
about over time, returning to the problem if and when any light is
Can you find a way of defining the number of fingers you multiply
and the numbers you add?
Discussion of complements of 10 first might support learners in
making the necessary connections.
Could you start at 16 on each hand? What adjustments would you need
How about 26, 36 etc?
Could you use 11 to 15?