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, ...

When you multiply decimals by integers (whole numbers), you can use everything you already know about multiplying multi-digit numbers. You can use written or mental methods to multiply decimals by ...