Adding and Subtracting a Positive Integer

To add a positive integer b to an integer a, move b units to the right-hand side of a on a number line. Consider a= 3 and b= 7. a= 3, b= 7 ⇓ 3+ 7=? The process of adding a and b will be illustrated using these values.

1

Plot a on a Number Line

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Begin by graphing a on a number line. In this case, the value of a= 3. Move 3 units to the right side of 0 to plot 3.

2

Move b Units to the Right-Hand Side of a

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Starting from a, move b units to the right to add b units to a. For this example, move seven units to the right of 3 to add 7 to 3.

The point is now at 10. This means that the sum of 3 and 7 is 10. 3+ 7=10

Subtracting a positive integer b from a is similar. In this case, move b units to the left-hand side of a on a number line. Consider the subtraction of b from a using the same example values. a= 3, b= 7 ⇓ 3- 7=? This process can be performed on the number line.

Now the point is at -4. The result of subtracting 7 from 3 is -4. 3- 7=-4 This process applies to adding or subtracting any positive integer b from a positive or negative integer a. The result can be a negative integer, a positive integer, or 0.