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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.

 
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