Subtracting Integers

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Subtracting Integers
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Where is the tallest building in the world?
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The tallest building in the world!
Nineteenth Century
Twentieth Century
The Eiffel Tower Paris, France 1889
The Petronas Towers Kuala Lumpar, Malaysia 1998
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What is the difference in height?
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The Petronas Towers are 683 feet taller than the
Eiffel Tower.
1667 984 683
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The Eiffel Tower is 683 feet shorter than the
Petronas Towers.
984 - 1667 -683
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In subtraction, two numbers are compared, and
their difference is found.
If the first number is greater than the number
subtracted, the difference is positive. 1667
984 683
If the first number is less than the number
subtracted, the difference is negative. 984
1667 -683
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5 3
five minus three
The difference between 5 and 3
5 is 2 greater than 3.
The difference will be positive because 5 is
greater than 3.
5 3 2
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3 5
three minus five
The difference between 3 and 5
3 is 2 less than 5.
The difference will be negative because 3 is less
than 5.
3 5 -2
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Subtraction Related Addition

5 - 3 2 5 2
3 - 5 -2 3 -2
-2 - (-6) 4 -2 4
-6 - (-2) - 4 -6 - 4
3 - (-4) 7 3 7
- 4 - 3 -7 - 4 -7
-3
-5
6
2
4
-3
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Rule for Subtracting Integers
Write related addition problem by
and
Add using rules for adding integers.
4 - 6
-2
-2 (-7)
-2
7
5
12
5 (-4)
5
4
9
-1 10
-1
(-10)
-11
8 12
8
(-12)
-4
-7 (-9)
-7
9
2
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SUBTRACTING INTEGERS

• We often think of subtraction as a take away
  operation.
• Which diagram could be used to compute
• 3 - 5 ?

3
5
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SUBTRACTING INTEGERS

• This diagram also represents 3, and we can take
  away 5.
• When we take 5 yellow tiles away, we have 2 red
  tiles left.

We cant take away 5 yellow tiles from this
diagram. There is not enough tiles to take away!!
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SUBTRACTING INTEGERS

• Use your red and yellow tiles to model each
  subtraction problem.

• -2 - -4 ?

ANSWER
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SUBTRACTING INTEGERS
Now you can take away 4 red tiles.
2 yellow tiles are left, so the answer is
This representation of -2 doesnt have enough
tiles to take away -4.
Now if you add 2 more reds tiles and 2 more
yellow tiles (adding zero) you would have a total
of 4 red tiles and the tiles still represent -2.
-2 - -4 2
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SUBTRACTING INTEGERS

• Work this problem.
• 3 - -5 ?

ANSWER
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SUBTRACTING INTEGERS

• Add enough red and yellow pairs so you can take
  away 5 red tiles.
• Take away 5 red tiles, you have 8 yellow tiles
  left.

3 - -5 8
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SUBTRACTING INTEGERS

• Work this problem.
• -3 - 2 ?

ANSWER
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SUBTRACTING INTEGERS

• Add two pairs of red and yellow tiles so you can
  take away 2 yellow tiles.
• Take away 2 yellow tiles, you have 5 red tiles
  left.

-3 - 2 -5