Visualising numbers

During my teacher training I stumbled upon an intriguing piece of equipment - the Slavonic abacus. Though it was never part of the National Curriculum and I didn't used it in my classroom teaching practice it would have been interesting to have introduced it into an ordinary maths lesson.

The abacus has 100 beads which are subdivided into quarters. Each quarter is coloured differently to its adjacent quarters. The abacus works on the principle of 'fives', allowing us to calculate quickly by breaking numbers down into clearly identifiable chunks - so 5 rows of 5 makes 25 and 4 lots of 25 make 100 - all you need to know is your five times table - simple.

The abacus at rest

And here's how to calculate  6 x 8:

 

We can start by making 6 rows of  8 beads (these beads have been moved to the left). We now have four blocks of different coloured beads: 5 blue columns of 5 beads, 3 yellow columns of 5 beads and 1 row of 5 yellow beads plus a 'remainder' of three blue beads. Adding up all these fives makes 45 and the remaining 3 makes 48.

 

 

If you feel like playing with the abacus there's one here (you'll need Adobe Shockwave)