Thursday 7 July 2011

Adding and Subtracting One-Digit Numbers (4)

Example :    3 - 2 = 1 

Step 1: Set 3 with the thumb. 



Step 2: Subtract 2 by moving down two 1-unit beads with the index finger. 



Note: This example illustrates the procedure used in subtracting one or more 1-unit beads. The problems to which this procedure applies are:  

2—1
3—1
4—1
6—1
7—1
8—1
9—1  
3—2
4—2 
7—2
8—2
9—2   
4—3  
8—3
9—3       
9—4

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