As you know, I am a bit of a Japanese abacus fanatic. This lead me to a fascinating method of multiplying using straight lines. Here’s how it works.

We’ll take an example of 123 x 332

Draw parallel lines representing the number 123

Next draw a similar set of lines in the other direction representing 332

Now, all you have to do is separate the groups of numbers as I have done below

Count the intersections in each group.

This gives you 3 9 17 13 6

Carry the 10 of the 17 left to add it to the 9 and leave 7.

Carry the 10 of the 13 to the left and add it to the 7 giving 8 and leaving 3

And finally where the 9 became a 10, carry that to the left and add it to the 3 to make 4 leaving 0

Answer 40836

Check it with your calculator, although who needs a calculator now?

There are added techniques. Notably a number between 5 and 9 in the starting sum is drawn with a different colour representing the 5, just to reduce the number of lines that have to be drawn.