Addition and Subtraction of Directed Numbers

In a horizontal number line:

1. When adding, start from the first number, count right along the number line.

2. When subtracting, start from the first number, count left alone the number line.

Note: In a horizontal number line, numbers to the right of zero are positive, and numbers to the left are negative.

Worked Example 10.2.1:

Use number line to find the value of:

i. 0 +  6
ii. 2 + 7
iii. -6  –  4
iv. -8  +  11
v. -5   +  4
vi. -3  –  5

i. 0   +   6

Solution

 *Start at 0, count 6 places to the right to end up at 6.

So,   0  +  6   =  6

ii. 2   +   7  

Solution