Transcript Solving Addition and Subtraction Equations An equation is a

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