- A number line is a line with evenly spaced marks that represent numbers like integers, fractions, and other quantities. - Numbers can be graphed on a number line by placing a point at the mark corresponding to the number. - Movement right on the number line represents increasing or positive numbers, while movement left represents decreasing or negative numbers.

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A number line is a line with marks on it that are placed at
equal distances apart.
One mark on the number line is usually labeled zero and then
each successive mark to the left or to the right of the zero
represents a particular unit such as 1 or ½.
On the number line above, each small mark represents ½
unit and the larger marks represent 1 unit.

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Number lines can be used to represent:
A. Whole numbers – The set {0, 1, 2, 3, …}.
B. Positive numbers – any number that is greater than
zero.
C. Negative numbers – any number that is less than zero.
D. Integers – The set of numbers represented as
{…, -3, -2, -1, 0, 1, 2, 3, …}
The arrows at the ends of the number line show that the
number line continues in both directions without ending.

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A number can be graphed on a number line by placing a point
at the appropriate position on the number line.
Example
a) {4} (blue point)
b) {integers between –10 and –5} (purple)

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Name the set of numbers that is graphed.
{-8, -4, 1, 5, 8}

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Movement to the right on the number line is in the positive
direction (increasing).
Movement to the left on the number line is in the negative
direction (decreasing).
Make the following moves on the number line.
Start at 5 and move left 7.
Where did you stop? -2
How can we represent this mathematically? 5 + (-7) = -2

7. Graph the set of numbers on a number line. Write two
inequalities comparing the two numbers.
1. -2, 7 2. -9, -4 3. 3, 8
Find each sum using a number line.
4. 3 + 7 5. -1 + (-7)
6. -4 + 12 7. -9 + 5
8. -6 + 6

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− <2 7 7 2> −
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− < −9 4 − > −4 9
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3 8< 8 3>

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3 + 7
Start at 3 and move 7 places to the right.
3 + 7 = 10

10. -1 +(-7)
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Start at -1 and move 7 places to the left.
-1 + (-7) = -8

11. -4 + 12
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Start at -4 and move 12 places to the right.
-4 + 12 = 8

12. -9 + 5
-5 50 10-10
Start at -9 and move 5 places to the right.
-9 + 5 = -4

13. -6 + 6
-5 50 10-10
Start at -6 and move 6 places to the right.
-6 + 6 = 0