Solving addition and subtraction equations power point copy
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![Page 1: Solving addition and subtraction equations power point copy](https://reader033.fdocuments.net/reader033/viewer/2022061121/5467f24faf7959b65d8b5de4/html5/thumbnails/1.jpg)
Solving Addition and Subtraction Equations
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An equation is a
mathematical sentence
that contains an equal sign.
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The expression on the left and right side of the equal
sign are equivalent. One or
both sides may contain a variable.
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A variable is a letter or
symbol that stands for a
number.
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To solve an equation, you
must find what the variable
represents so that the two
parts are equal.
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Equations are like balance scales. In order to keep a scale balanced you must have the same amount of weight on both sides.
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If I took one block away from the left side, what would I have to do to keep
the scale from tipping?
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If I added 6 more apples to the right side, how could I keep the scale from
tipping?
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To keep an equation equal, we must do exactly the same
thing to each side of the equation. If we
add a number to one side, we must add
that same number to the other side and
vice versa.
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Addition and subtraction are called “inverse operations”.
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Multiplication and
division are inverse
operations, too!
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for Solving Addition and Subtraction Equations
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1. Look to see what side the variable
is on.
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2. Decide what
operation is being shown.
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3. Do the inverse of
that operation to both sides.
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4. Write what
number the variable
stands for (ex: a = 2).
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5. Check the solution by “substituting” the number back into the equation to see if the sides are equivalent.
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Example 1 (bar model) m + 18 = 34 Look for variable
Do the inverse What number does m represent?
m = 16
Substitute in m
16 + 18 = 34
34 = 34
Solution is correct!
m 18
34
16 18
34
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Example 1m + 18 = 34 Look for variable
-18 -18 Do the inverse
m = 16 Write what m is
m + 18 = 34
16 + 18 = 34 substitute in m
34 = 34 Solution is correct!
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Always remember to check your solution to the
equation.
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Example 2 68 = y + 43 Look for variable
-43 -43 Do the opposite
25 = y Write what y is
68 = y + 43
68 = 25 + 43 Plug in y
68 = 68 Solution is correct!
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Example 3 t - 14 = 22 Look for variable
+ 14 +14 Do the inverse
t = 36 Write what t is
t - 14 = 22
36 - 14 = 22 Substitute in t
22 = 22 Solution is correct!
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Try These...1. r + 5 = 18
2. m - 26 = 59
3. 102 = x - 15
4. a + 39 = 56
r = 13
m = 85
117 = x
a = 17
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Prediction:You will show all
of the steps (including
checking) as you have been shown
today
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Are there any questions
about solving addition or subtraction equations?