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2.
An equation is
a
mathematical
sentence that
contains an
3.
The expression on the
left and right side of
the equal sign are
equivalent. One or
both sides may
contain a variable.
4.
A variable is a
letter or
symbol that
stands for a
number.
5.
To solve an
equation, you must
find what the
variable represents
so that the two
parts are equal.
6.
Equations are
like balance
scales. In order
to keep a scale
balanced you
must have the
same amount of
weight on both
7.
If I took one block away from the left
side, what would I have to do to keep
the scale from tipping?
8.
If I added 6 more apples to the right
side, how could I keep the scale from
tipping?
9.
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.
10.
Addition and
subtraction are called
“inverse operations”.
11.
Multiplicatio
n and
division are
inverse
operations,
too!
12.
for Solving Addition
and Subtraction
Equations
17.
5. Check the
solution by
“substituting” the
number back into
the equation to
18.
Example 1 (bar model)
m + 18 = 34
m
18
34
Look for variable
Do the inverse
What number does m represent?
m = 16
Substitute in m
16
18
34
16 + 18 = 34
34 = 34
Solution is correct!
19.
Example 1
m + 18 = 34
-18 -18
m = 16
Do the inverse
m + 18 = 34
16 + 18 = 34
34 = 34
substitute in m
Look for variable
Write what m is
Solution is correct!
20.
Always remember to
check your solution
to the equation.
21.
Example 2
68 = y + 43
-43
-43
Look for variable
25 = y
68 = y + 43
68 = 25 + 43
68 = 68
Write what y is
Do the opposite
Plug in y
Solution is correct!
22.
Example 3
t - 14 = 22
+ 14 +14
t = 36
Do the inverse
t - 14 = 22
36 - 14 = 22
22 = 22
Substitute in t
Look for variable
Write what t is
Solution is correct!
23.
Try These...
1.
2.
3.
4.
r + 5 = 18
m - 26 = 59
102 = x - 15
a + 39 = 56
r = 13
m = 85
117 = x
a = 17
24.
Prediction:
You will show all
of the steps
(including
checking) as you
have been shown
today
25.
Are there any
questions
about solving
addition or
subtraction
equations?
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