Fact Field

Here is the whole times table: one hundred squares. Fold it and see that 3 × 7 and 7 × 3 are one fact — so there are only fifty-five to know. A square fills in when you use Arlo’s or Parti’s way on it.

The oldest decimal multiplication table we know of is on bamboo strips from China, about 2,300 years old. Yours lives on this device.