Transcript 2.8 Division Equations

Division Equations
Unit 2.8
Pages 81-83
Warm Up
Problems
Solve for the missing variable?
1. 5x = 20
X=4
2. 7n = 84
N=12
3. 18 = y - 4
Y=22
4. 21 = n + 3
N=18
Using the inverse of
Division for equations.
3x2 = 6
Objective:
6 3=2
Students will be able to solve
whole number division problems using the
inverse of division which is multiplication, then
check their answers.
We show “division” in many ways.
Divided by
X 18
Divided by
18 x
The trick with a Division
Problems is to remember
to say “this number
(whatever it may be) IS
DIVIDED BY this number?
This will help you place the
number in the right spot in
the Division problem.
18
x
Divided by
18 divided
by x
We know that Multiplication is the inverse (or
opposite) of Division because when we write the
fact families for numbers, they appear that way.
3x2=6
6/3=2
6/2=3
2x3=6
Inverse!
The inverse of Division is
Multiplication. Just remember to
“undo” what you just did by saying
WHAT YOU DO TO
ONE SIDE, YOU HAVE
TO DO IT TO THE
OTHER SIDE!
http://www.youtube.com/watch?v=rkOzTmfUv1A
Before we can try to do the inverse of
division we must know what a
RECIPROCAL is
Who can do a Hand Stand?
Come on up and try it! Just say a whole
Number then
Reciprocal!
What are you now?
Lets try Some out but write them as fractions!!!!!!!!!!!!
We use a fraction bar to show how we will perform
division and we show multiplication using the
RECIPROCAL .
Isolate the
variable
y
=
4
(5)
(5)
5
1
1
y = 20
Bring down
the y and
Product
Perform
the
reciprocal
to both
sides
Now we have to Check it.
20
4 y = 4
5
YES!
Remember
to keep
everything
balanced.
Preform the
RECIPROCAL
(opposite) to
get a
solution
12
Now check it by putting the solution
back into the equation
z=48
1z
4
Remember to
keep
everything
balanced.
Preform the
RECIPROCAL
(opposite) to
get a solution
1n
2
Now check it by putting the solution
back into the equation
n=100
50
Remember to
keep
everything
balanced.
Preform the
RECIPROCAL
(opposite) to
get a solution
20
Now check it by putting the solution
back into the equation
c=60
1c
3
Solve each
equation
and check
your
answers.
n=35
Now you try it!
Share the answer with a partner.
1n = 5
7
Solve each
equation
and check
your
answers.
x=27
Now you try it!
Share the answer with a partner.
1x = 3
9
Solve each
equation
and check
your
answers.
p=78
Now you try it!
Share the answer with a partner.
13 = 1p
6
Solve each
equation
and check
your
answers.
r=108
Now you try it!
Share the answer with a partner.
9 = 1r
12
Now you try it!
Share the answer with a partner.
3 = 1y
4
Y=12
Now you try it!
Share the answer with a partner.
14 = 1z
2
Z= 28
Now you try it!
Share the answer with a partner.
7 = 1r
9
R=63
Now you try it!
Share the answer with a partner.
12 = 1j
3
J=36
Now you try it!
Share the answer with a partner.
9 = 1x
5
X=45
Now you try it!
Share the answer with a partner.
1s = 4
10 40
S=1
At Barker Park the Aspen Trees are
1/3 the height of the Pine trees.
If the Aspen trees are 14 feet tall,
how tall are the Pine trees?
Write a division equation, and solve
Because we are comparing things, we know that we
will have an equation with an equal sign in it.
Aspen Trees
14 ft.
Pine Trees
p1/3
Multiplication is the Inverse of Division. When we
multiply 3 to both sides of the equation we “undo”
the Division. This helps us find our solution.
(3)14 = 1p(3)
3
1
1
42 = pine
Pine Trees are 42 feet tall
#9) The amount of time Lydia spent
mowing her lawn was 1/3 the time she
spent planting her flowers.
If Lydia spends 30 minutes mowing her
lawn, how much time did she spend
planting her flowers?
Write a division equation, and solve
Because we are comparing things, we know that we
will have an equation with an equal sign in it.
Mowing
30 min
Planting
p1/3
Multiplication is the Inverse of Division. When we multiply 3 to
both sides of the equation we “undo” the Division. This helps
us find our solution.
(3) 30 = p (3)
3 1
1
90 = planting
It took Lydia 90 min to
plant her flowers
2.8 Homework
(pg 82-83): Due Thursday 22nd

10-24
10-18