Lesson Presentation

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Warm Up
Problem of the Day
Lesson Presentation
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Warm Up Solve. 1. x 3 11 2. 18 x
4 3. 42 4. 2x 52 5. x 82 172
x 14
x 14
x
x 294
7
x 26
x 254
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Problem of the Day Find the missing entries in
the magic square. 11.25 is the sum of every row,
column, and diagonal.

3.75 5.25
6
3
6.75
1.5
2.25
0.75
4.5
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Learn to solve equations involving decimals.
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You can solve equations with decimals using
inverse operations just as you solved equations
with whole numbers.
45.20 m 69.95
45.20
45.20
m 24.75
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Additional Example 1A Solving One-Step Equations
with Decimals Solve the equation. Check your
answer.
k 6.2 9.5
6.2 is subtracted from k.
k 6.2 9.5
Add 6.2 to both sides to undo the subtraction.
6.2
6.2
k 15.7
Check
k 6.2 9.5
Substitute 15.7 for k in the equation.
15.7 is the solution.
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Additional Example 1B Solving One-Step Equations
with Decimals Solve the equation. Check your
answer.
6k 7.2
k is multiplied by 6.
6k 7.2
Divide both sides by 6 to undo the multiplication.
6k 7.2
k 1.2
Check
6k 7.2
Substitute 1.2 for k in the equation.
1.2 is the solution.
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Additional Example 1C Solving One-Step Equations
with Decimals Solve the equation. Check your
answer.
m
0.6
m is divided by 7.
7
Multiply both sides by 7 to undo the division.
7
0.6
7
m 4.2
Check
Substitute 4.2 for m in the equation.
4.2 is the solution.
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Check It Out Example 1A Solve the equation.
Check your answer.
n 3.7 8.6
3.7 is subtracted from n.
n 3.7 8.6
Add 3.7 to both sides to undo the subtraction.
3.7
3.7
n 12.3
Check
n 3.7 8.6
Substitute 12.3 for n in the equation.
12.3 is the solution.
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Check It Out Example 1B Solve the equation.
Check your answer.
7h 8.4
h is multiplied by 7.
7h 8.4
Divide both sides by 7 to undo the multiplication.
7h 8.4
h 1.2
Check
7h 8.4
Substitute 1.2 for h in the equation.
1.2 is the solution.
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Check It Out Example 1C Solve the equation.
Check your answer.
w
0.3
w is divided by 9.
9
Multiply both sides by 9 to undo the division.
9
0.3
9
w 2.7
Check
Substitute 2.7 for w in the equation.
2.7 is the solution.
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Additional Example 2A Measurement Application
The area of Emilys floor is 33.75 m2. If its
length is 4.5 meters, what is its width?
area length width
33.75 4.5 w
Write the equation for the problem. Let w be the
width of the room.
33.75 4.5w
33.75 4.5w
Divide both sides by 4.5 to undo the
multiplication.
4.5
4.5
7.5 w
The width of Emilys floor is 7.5 meters.
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Additional Example 2B Measurement Application
If carpet costs 23 per square meter, what is the
total cost to carpet the floor?
total cost area cost of carpet per square
meter
Let C be the total cost. Write the equation for
the problem.
C 33.75 23
Multiply.
C 776.25
The cost of carpeting the floor is 776.25.
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Check It Out Example 2A
The area of Yvonnes bedroom is 181.25 ft2. If
its length is 12.5 feet, what is its width?
area length width
181.25 12.5 w
Write the equation for the problem. Let w be the
width of the room.
181.25 12.5w
181.25 12.5w
Divide both sides by 12.5 to undo the
multiplication.
12.5
12.5
14.5 w
The width of Yvonnes bedroom is 14.5 feet.
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Check It Out Example 2B
If carpet costs 4 per square foot, what is the
total cost to carpet the bedroom?
total cost area cost of carpet per square foot
Let C be the total cost. Write the equation for
the problem.
C 181.25 4
Multiply.
C 725
The cost of carpeting the bedroom is 725.
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Insert Lesson Title Here
Lesson Quiz
Solve each equation. Check your answer. 1. x
3.9 14.2 2. 8.3 3. x 4.9 16.2 4. 7x
47.6 5. The area of the floor in Devons room is
35.7 m2. If the width is 4.2 m, what is the
length of the bedroom?
x 18.1
x 33.2
x 21.1
x 6.8
8.5 m