10/21/08
Solve with multiplication or division (2-12 B)
#26
Warm-up: Solve the following
A.
E.
B.
x+5=9
C.
F.
x – 34 = 72
D.
G.
Assignment:
(2-12) B evens or odds AND (2-12) puzzle all
Show all steps on graph paper in required format.
Quiz corrections are due tomorrow for retakes.
Math binder scores will be collected tomorrow for lessons #11- #21
124 = x – 39
10/21/08
Solve with multiplication or division (2-12 B)
#26
Warm-up
A.
E.
B.
x + 5= 9
-5 -5
X =4
C.
F.
D.
x – 34 = 72
+34 +34
x
= 106
Assignment:
(2-12) B evens or odds AND (2-12) puzzle all
Show all steps on graph paper in required format.
G.
124 = x – 39
+39
+39
163 = x
Quiz corrections are due tomorrow for retakes.
Math binder scores will be collected tomorrow for lessons #11- #21
Solving Equations by
2-12 Multiplying or Dividing
Like addition and subtraction, multiplication
and division are inverse operations. They
“undo” each other.
•
÷
Course 2
Solving Equations by
2-12 Multiplying or Dividing
Additional Example 1: Solving an Equation by
Multiplication
Solve the equation h = 13. Check your answer.
2
h
2 = 13
(2) h
2 = 13(2)
h = 26
Check
Think: h is divided by 2, so
multiply both sides by 2 to
isolate h.
h
2 = 13
26 ?
= 13
2
?
13 = 13 
Course 2
Substitute 26 for h.
26 is a solution.
Solving Equations by
2-12 Multiplying or Dividing
MULTIPLICATION PROPERTY OF EQUALITY
You can multiply
both sides of an
3·4=
12
equation by the
2 · 3 · 4 = 2 · 12
same number,
6·4=
24
and the statement
will still be true.
x = y
zx = zy
If a variable is divided by a number, you can
often use multiplication to isolate the variable.
Multiply both sides of the equation by the
number.
Course 2
Solving Equations by
2-12 Insert
Lesson
Title Here
Multiplying
or Dividing
Try This: Example 1
x
Solve the equation 5 = 30. Check your answer.
x
= 30
5
Think: x is divided by 5, so
(5) x
5 = 30(5)
x = 150
Check
multiply both sides by 5 to
isolate x.
x
5 = 30
150 ?
= 30
5
?
30 = 30 
Course 2
Substitute 150 for x.
150 is a solution.
Solving Equations by
2-12 Multiplying or Dividing
Additional Example 2: Solving an Equation by
Division
Solve the equation 51 = 17x. Check your
answer.
Think: x is multiplied by 17,
51 = 17x
so divide both sides by 17 to
51 = 17x
isolate x.
17
17
3=x
Check
51 = 17x
?
51 = 17(3)
?
51 = 51
Course 2
Substitute 3 for x.
3 is a solution.
Solving Equations by
2-12 Multiplying or Dividing
DIVISION PROPERTY OF EQUALITY
You can divide
both sides of an
equation by the
same nonzero
number, and the
statement will still
be true.
5 · 6 = 30
5·6
30
=
3
3
5 · 6 = 10
3
5 · 2 = 10
Remember!
You cannot divide by 0.
Course 2
x=y
x= y
z
z
z≠0
Solving Equations by
2-12 Insert
Lesson
Title Here
Multiplying
or Dividing
Try This: Example 2
Solve the equation 76 = 19y. Check your
answer.
Think: y is multiplied by 19,
76 = 19y
so divide both sides by 19 to
76 = 19y
isolate y.
19
19
4=y
Check
76 = 19y
?
76 = 19(4)
?
76 = 76
Course 2
Substitute 4 for y.
4 is a solution.
Solving Equations by
2-12 Multiplying or Dividing
Additional Example 3 Continued
Beats in 10s
b
times 6
· 6
6b = 78
6b = 78
6
6
b = 13
= beats per minutes
=
78
Think: b is multiplied
by 6, so divide both
sides by 6 to isolate b.
Trevor’s heart beats 13 times 10 seconds.
Course 2
Solving Equations by
2-12 Multiplying
Insert Lesson
Title Here
or Dividing
Lesson Quiz: Part 1
Solve the equation. Check your answer.
1. 12 = 4x
x=3
2. 18z = 90
z=5
3. 12 = x
4
x = 48
4. 840 = 12y y = 70
5. h = 9
22
Course 2
h = 198
10/21/08
Solve with multiplication or division (2-12 B)
• Show all steps on graph paper in required format.
(2-12) B evens or odds
AND
(2-12) puzzle all
Quiz corrections are due tomorrow for retakes.
Math binder scores will be collected tomorrow for lessons
#11- #21
#26