Adding and Subtracting One-Digit Numbers (7)

Example :    4 + 1 = 5 

Step 1: Set 4. 

Step 2: Move down 5 first and 4 next in close succession with the index finger. 

Note: This example illustrates the procedure used in setting 5 when the addition of two numbers makes 5. The problems to which this procedure applies are:  

4+1    

3+2     

2+3     

1+4 

Example :   5 —1 = 4 

Step 1: Set 5. 

Step 2: First move up 4 with the thumb, and then move up 5 with the index finger in close succession. Flick the thumb and the index finger with the idea of performing the two motions at the same time. 

Note: This example illustrates the procedure of subtracting a number from 5. The problems to which this procedure applies are: 

5—3 

5—4   

6—3   

7—4          

8—4 

Example :   3 + 7 = 10 

Step 1: Set 3 on a unit rod. 

Step 2: In close succession, first move down then 3 on right column with the index finger, and then move up 1 on the tens’ rod (second right column), with the thumb. Flick the index finger and the thumb in a twisting manner so that you may perform the two motions at the same time. 

Note: This example shows how to set 10 when it is the sum of two digits. This procedure requires the subtraction of one or more 1-unit beads. Problems to which applicable: 

1+9 

2+8 

3+7 

4+6 

Example :    10 — 7 = 3 

Step 1: Set 10. This is done by simply moving up one bead on the tens’ rod (second right column). 

Step 2: First remove the 10 by moving down the 1 on the tens’ rod with the index finger, and then move up 3 on the unit rod (1^st right column) with the thumb. 

Note: This example shows how to subtract 10 and add one or more 1-unit beads. Problems to which such procedure applies: 

10—9  

10—8  

10—7 

10—6