The array can be shown as 5 groups of 3 showing that 5 x 3 = 15. Or it could be shown as 3 groups of 5 showing that 3 x 5 = 15. This demonstrates that multiplication is commutative. Image caption, ...

You can solve a lot of multiplication calculations by working things out in your head. Knowing your times table facts is a great way to multiply smaller numbers in your head. However, there are also ...