Chapter 1Section 5: Adding IntegersSection 6: Subtracting IntegersBy Ms. Dewey-Hoffman, 2009 http://msdhpowerpoints.blogspot.com/

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Rules for Adding Integers

Adding Integers with the Same Sign:

– The sum of two positive integers is positive.

– The sum of two negative integers is negative.

• Example: -12 + (-31) = -43

• Example: 22 + 16 = 28

Adding Integers with Different Signs:

– Find the difference (subtraction) of their absolute values. The answer has the sign of the integer with the greater absolute value.

• Example: -125 + 35 =

|-125| + |35| =

125 – 35 = 90

Biggest number is negative, so the answer is negative. -90

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Addition of Opposites It’s a property!

– The sum of an integer and it’s opposite is zero.

• Example: 7 + -7 = 0

Adding Integers

– Turn it into a word problem and say it out loud.

• Example: -1 + 4, You owe me 1 dollar, you have 4 to pay me back, how much do you have left over? 3.

• Example: 7 + (-3), You have 7 dollars, you buy something for 3 dollars, how much do you have left? 4.

– You give up negative numbers and you keep positive numbers.

– Example Problems:

• -2 + (-2) =

• 2 + (-6) =

• -4 + 9 =

• -5 + (-1) =

Adding Integers

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Adding Integers with Different Signs: Example Problems Remember: Find the difference of their absolute value. The sign of the

number with the greatest absolute value gives the sign of the answer.

Also: Go left to right when all you’re doing is adding and subtracting!

1 + (-3) + 2 + (-10) =

-250 + 200 + (-100) + 220 =

The elevation of a monitor in Pinon Flat, California, is 1,696 meters higher than the monitor in Hockley, Texas (at -416 meters). Find the elevation of the monitor in Pinon Flat.

1) Write an expression.

2) Solve.

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Subtracting Integers Add Its Opposite

– Turn the subtraction sign into addition and take the OPPOSITE of the second number.

– Then treat the problem as an addition problem. (Difference of absolute value, etc).

Example Problems:

– 2 – 5 =

– 44 – 100 =

– 32 – (-3) =

– -40 – 66 =

– 2 – 48 =

– The lowest temperature ever recorded in Antarctica was -89°C. The lowest temperature ever recorded on the moon was about -170°C. What is the difference in the temperatures?

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Assignment #3

Pages 26-27: 21-32 all, 54-60 even.

Pages 31-32: 20-36 even, 57-61 all.

No extra credit today.

Remember to show work, set up your page correctly and box your answers!

Due September 4th, 2009.