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?