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Solving Addition and Subtraction Equations
Which word do you think
“Equation” has a connection
to?
YOU’RE CORRECT!
An equation is a
mathematical sentence
that contains an equal sign.
The part on the left side of the equal
sign has the same value as the part on the right side. One or both sides
may contain a variable.
What is a variable?
A. A number that changes constantly.B. A letter or symbol that stands for an unknown number. C. A number that varies as you move away from zero.
YOU’RE CORRECT!
A variable is a letter or
symbol that stands for an
unknown 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” because they can ‘undo’
each other.
What are the other two 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.
Don’t forget INTEGER rules!!!!!
4. Write what
number the variable
stands for (ex: a = 2).
5. Check the solution by “plugging” the number back into the equation to see if the sides are equal.
Example 1m + 18 = 34 Look for variable
-18 -18 Do the opposite
m = 16 Write what m is
m + 18 = 34
16 + 18 = 34 Plug in m
34 = 34 Solution is correct!
If you check your solution and you do not come out with the same numbers, then your solution is
not correct. Therefore, you
must rework the problem.
Always check your answers to
equations. It is the only way to make
sure you get a problem correct.
Why miss a problem when you can get all of them
correct?
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!
Example 3 t - 14 = 22 Look for variable
+ 14 +14 Do the opposite
t = 36 Write what t is
t - 14 = 22
36 - 14 = 22 Plug in t
22 = 22 Solution is correct!
Prediction:You will show all
of the steps (including
checking) as you have been shown
today or ELSE…………..
Are there any questions
about solving addition or subtraction equations?