People in China started to use an abacus to help them with math problems maybe as early as 500 BC. Nobody knows whether somebody in China invented the abacus. Maybe they learned about it from people in the Persian Empire (modern Iran), who started using the abacus about the same time. Whoever invented the compass probably started by counting on their knuckles. You have twelve knuckles on each hand, so you can use them to count to 24. Twenty-four has a lot of factors, so you can do a lot of arithmetic quickly – as quickly as on a calculator – if you know how. An abacus may have started as a sort of artificial set of hands. By the 100s AD, accountants and business people were using the abacus in the Roman Empire, too.
Find out how to use an abacus for adding big numbers quickly.
You can make your own abacus. Start with a wooden picture frame. Fit another piece of wood across it the long way so it fits tightly. You can glue it and nail it in place with small nails. Drill small holes all along the inside edges, and cut wires to fit. String beads on the wires and jam them into the holes.
Science in Ancient China, by George Beshore (1998). .
The Ambitious Horse: Ancient Chinese Mathematics Problems, by Lawrence Swienciki (2001).
Ancient China: 2,000 Years of Mystery and Adventure to Unlock and Discover (Treasure Chest), by Chao-Hui Jenny Liu (1996). Lots of activities , including a Chinese calligraphy set.
A History of Chinese Mathematics, by Jean-Claude Martzloff (1997). For adults. Explains the differences between Chinese and Euclidean (Greek) mathematics.
Zero: The Biography of a Dangerous Idea, by Charles Seife and Matt Zimet (2000).