Il regolo calcolatore

Calculation ability is not an innate gift, but, thanks to proper training, it can be developed.
The slide rule is a simple tool that allows you to perform calculations quickly. The ruler is made up of two strips: one upper (sliding) and one lower fixed.
To add or subtract, slide the upper strip until the zero is above the first addend or minuend: in correspondence with the second addend or minuend, the result will be found on the lower strip.