Then and Now- Simple Arithmetic Calculation

Then:

Ancient Methods of Performing Simple Calculations.
Image Sources: Google Images
From left to right:
1. Pebbles 2.Strings 3.Counting board 4.Abacus 5.Napier's Bones.

Now:

Modern Tools for Performing Simple Calculations
Image(s) Sources: Google Images
From left to right:
1. Smart watch 2. Casio Calculator 3. Mobile phone