From a few fragments out of a collection of 23-century-old bamboo strips, historians have pieced together what they say is the world's oldest example of a multiplication table in base 10. Five years ...

The Tsinghua table places factors across the top row and down the far right column. From left to right, or from bottom to top, respectively, the values are ½, 1, 2 . . . 9, then 10, 20 . . . 90. The ...