Download equation - TeacherWeb

Writing and Evaluating
Addition and Subtraction
Equations
What is an equation?
• An equation is a mathematical sentence
that has an equal sign.
• An equation has ONLY one solution.
• A solution is an answer that can be
substituted in for a variable to make an
equation true.
We can use inverse operations to write and solve
addition and subtraction equations.
Inverse operations undo each other.
For example, to solve an addition equation, use
subtraction.
When writing equations, a variable should
ALWAYS be paired with a number and an
operation! Your variable should NEVER be by
itself on one side of the equals sign!
Yes: 4 + y = 10
NO!!!! 4 + 6 = y
Subtraction Property of Equality
If you subtract the same number from each side of an
equation, the two sides remain equal.
Addition Property of Equality
If you add the same number from each side of an
equation, the two sides remain equal.
(a) 3 + x = 10
(b)
(c)
9.5 + x = 14.3
¼+x=¾
(d) 13 = x + 9
(e) x + 9 = 18
(f) X + 2/7 = 5/14
x=7
x = 4.8
x=½
x=4
x=9
x = 1/14
(b) x – 7 = 12
(b) x – 17.06 = 13
(c) 3.86 = x – 5.97
(d) 34 = x – 8
(e) x – 9.24 = 25.02
(f) X – 3/18 = 11/18
x = 19
x = 30.06
x = 9.83
x = 42
x = 15.78
x = 14/18
You have 10 minutes left at a parking
meter. After you put in a quarter, you
have 25 minutes left. Write and solve an
equation to find q, the number of minutes
a quarter is worth.
You eat 9 strawberries from a
carton. There are 12
strawberries left. How many
strawberries were in the
carton?
Write and solve an equation
for the situation.
Your class is planting trees.
You have planted 17 trees.
You all have 14 tress left to
plant. Write and solve an
equation to find the number of
trees the class started with.
This month you have talked 153
minutes on your cell phone. You
can use 250 minutes before you
have to pay extra fees. Write and
solve an equation to find the
number of minutes, m, before you
have to pay extra fees.
You are delivering newspapers on your
paper route. You have to deliver to 8
more houses. You have already
delivered to 21 houses. How many
houses are on your route?
Write and solve an equation for the
situation.
A video game has 16 levels. You
have reached level 5. Write and
solve an equation to find the number
of levels you have left.
End of today’s lesson
Solve the following equations.
x + 18.9 = 46.3
27.4
p – 2.12 = 41.73
43.85
4 ½ + p = 7 3/10
2 4/ 5
5¾-y=4¼
1½
You have lost track of how many softball games you have
played this season. You know your team won 12 games.
Your friend reminds you that your team lost 9 games. How
many games did your team play?
Write and solve an equation for the situation.
You buy a shirt for $17.45. You give the clerk a $20 bill.
How much change do you get back?
Write and solve an equation for the given situation.