In the first chapter entry on representing directed numbers, Is it Positive or Negative?, we discussed how numbers move along a number line. Remember, as we move to the right along the number line, the numbers get bigger or grow. So when we see a positive number, the plus sign is an operator telling us that the total is getting bigger and moving to the right along the number line.

## Reading number sentences

The first number in an expression tells us the starting point on our number line. The operator (something like + or -) and the next number tell us how many places to move along the number line. When we are adding positive integers, we move to the right along the number line.

#### Examples

##### question 1

Here is an example of adding integers.

**Evaluate**: $5+3$5+3

**Think**:** **Start at $5$5, then move $3$3 spaces to the right along the number line.

**Do**: $5+3=8$5+3=8

Now let's look at an example that uses negative numbers:

##### question 2

**Evaluate**: $-3+2$−3+2

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##### Question 3

What about when the negative number has a bigger size than the positive number?

**Evaluate**: $-15+7$−15+7

**Think**: Start at $-15$−15, then move $7$7 spaces to the right along the number line.

Or, we could rearrange the number sentence as $7-15$7−15.

**Do**: $-15+7=-8$−15+7=−8

#####

##### Question 4

Evaluate: $-16+2+3$−16+2+3

Check out this applet and see how numbers move along a number line when we add them: