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 ...

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.