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 ...

Find out what multiples are and how to sort multiples of 2 and 5. Doubling numbers Learn how to make doubles using ten frames, addition and multiplication. Counting in twos, threes, fives and tens ...

Start by completing the calculation using positive numbers first, then use the sign rules to find the sign of the answer. Image caption, This multiplication table includes both positive and negative ...

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.