Wild About Math! Making Math fun and accessible

A very clever calculator

Below is an image from Wikipedia of a calculating device invented in 1891, Genaille's rods. Each column in the image is a rod that can be placed wherever it's needed in a calculation.

The image shows how to easily calculate 52749x4.

Can you figure out how this arithmetic tool works?

Making a set of these rods would be a great enrichment project. Here is a template (in different sizes) that you or your children or students can print and mount onto cardstock to make your own set. You'll want to make a number of each of the rods so that you can multiply by numbers where one or more digits occurs more than once.