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What is an integer?An integer is any number from the set { . . . -3, -2, -1, 0, +1, +2, +3, . . . } where . . . means without end.

-9 -8 -7 -6 -5 -4 -3 -2 -1 0 +1 +2 +3 +4 +5 +6 +7 +8 +9

negative integers positive integers

Negative numbers are written with a - sign.

Positive numbers are written with or without a + sign.

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Numbers to the left of zero on the number line are negative integers.

-9 -8 -7 -6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 7 8 9

Numbers to the right of zero on the number line are positive integers.

negative integers positive integers

Zero is not positive or negative.

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Give the opposite of each situation.Up 7 floors Down 7 floorsNorth 15 miles South 15 milesLose 7 points Gain 7 pointsRight 3 blocks Left 3 blocksSpent $12 Earned $12

20 feet above sea level

20 feet below sea level

2° below zero 2° above zero

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Each integer has an opposite. Opposite integers are the same distance from zero on opposite sides of the number line. Zero is considered to be the starting point.

-7 +7

-9 -8 -7 -6 -5 -4 -3 -2 -1 0 +1 +2 +3 +4 +5 +6 +7 +8 +9

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Give the opposite of each integer.

-9 -8 -7 -6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 7 8 9

-7 ____+7+12 ____-1237 ____-37

-68 ____ 6825 ____-25-72 ____ 72

negative integers positive integers

-4 ____ 4 42 ____ -42

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Integers can be used to describe real life situations.

-9 -8 -7 -6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 7 8 9

What integer would show?The stock market up by 27 points +27The stock market down by 15 points -15A gain of 7 pounds +7A loss of 3 club members -3An increase of 17° in temperature 17A gain of 5 yards on a football play 5A loss of 12 yards on a football play -12

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-9 -8 -7 -6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 7 8 9

Erin got on an elevator and went up 9 floors. Express this number as an integer.

+9

9

-9 -8 -7 -6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 7 8 9

David lost 11 pounds. Express this number as an integer.

-11

10

-9 -8 -7 -6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 7 8 9

Kevin received a $200 bonus. Express this number as an integer.

+$200

11

-9 -8 -7 -6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 7 8 9

A scuba diver is 25 feet below sea level. Express this number as an integer.

-25

12

-9 -8 -7 -6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 7 8 9

The value of a stock decreased by $17. Express this number as an integer.

-17

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Which situation is represented by the integer +4?

4 degrees above normal

a discount of $4a loss of 4 pounds

4 degrees below normal

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Which situation is represented by the integer -8?

moving forward 8 feet

a decrease of $8a rise of 8°

8 feet above sea level

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Which situation is represented by the integer -12?

12 feet above sea level

going down 12 floorsa price increase of $12a deposit of $12

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Which situation is represented by the integer +35?

a loss of $35

going down 35 feeta $35 deductiona deposit of $35

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A football player caught the ball and started running straight toward the goal line. He gained 15 yards. Then, a player from the other team pushed him back 5 yards. The football player was able to gain 4 more yards, but he lost 5 yards again when he was tackled. Write the expression that shows how many yards the football player gained before being tackled.

15 - 5 + 4 - 5

18

During January, the low temperature for a Tuesday morning was -4°. The temperature rose 15° during the day. Then it fell 10° on Tuesday night. Write the expression to find the low temperature on Tuesday night.

-4 + 15 - 10

19

Gregory gave an oral report for history class. He received 40 points for creating a colorful poster as a visual aid. He lost 10 points because he forgot to turn in his written report in advance. He earned 50 points because all of the historical facts he used were accurate. He also earned 5 extra-credit points for good presentation skills. Write the expression that shows how many points he earned for his oral report.

40 - 10 + 50 + 5

20

Mark and his brother went to the park. Mark had 3 quarters in his pocket. He also found a nickel and a dime on the sidewalk where they were walking. Mark gave his brother 50 cents to pay for a snow cone. Write the expression that shows how many cents Mark had left.

75 + 5 + 10 - 50