Unlike Esa Helttula's other apps, which allow kids to practice specific skills through a no-nonsense kind of interface, Esa's latest app, for the iPad, gives kids a playground of sorts to play around ...

Q: How much is 230 times 10? A: The number of years humans have been calculating with decimals. A crack team of scholars in Beijing learned this last year when they solved a 23-centuries-old puzzle.

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 ...

THESE tables aim at popularising logarithms. Like other four-figure tables they give the logarithms of numbers from 1000 to 9999. While the ordinary tables give these in one opening of two pages by ...

A girl and a boy of eight and nine years old live in a lost village in the steppes. The school is four kilometers off-road. The boy's daddy dreams of building a snowmobile, and while the girl's mom ...

The 2,300-year-old matrix is the world's oldest decimal multiplication table. From a few fragments out of a collection of 23-century-old bamboo strips, historians have pieced together what they say is ...