Commutation

Put simply, the rule of commutation says that it does not matter in which order you perform certain mathematical operations.

In ADDITION, 6 + 5 gives the same result as 5 + 6

In MULTIPLICATION, 6 x 5 gives the same result as 5 x 6

The easiest way to demonstrate the rule (with regard to multiplication) is to encourage children to prove it for themselves.

Draw 20 dots - neatly arranged as in the diagram.  Count the dots and visibly make a note of the number.

Using a coloured pencil, children should draw lines to show FIVE groups of FOUR.  Point out that "Five groups of four make twenty."

Write 5 x 4 = 20

Now, using the same diagram and a different coloured pencil, draw lines to show FOUR groups of FIVE.  Point out that "Four groups of five make twenty."

Write 4 x 5 = 20

Repeat with different numbers of dots.