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```					Please Turn Off Your Cell Phone!!!

For an emergency call, please leave the room before
answering the phone!

Thank you for respecting your classmates!!!
Section 8.2

Adding and Subtracting Decimal
Expressions
Adding + Subtracting Decimals

1. Rewrite so the numbers have the same
amount of decimal places.
2. Line up the numbers’ decimal places
vertically.
3. Add or subtract as normal.
Example
Add: 40 + 8.77 + 0.9

1
Ans:          40.00
8.77
+     0.90
49.67  Answer
You Try!!!
Add or Subtract:

1.   15 + 2.73 – 0.727

2.   -8.68 – 9.1
Section 8.3

Multiplying and Dividing Decimals
Multiplying Decimals

1. Multiply as normal
2. Add decimal places of original numbers
to find decimal place of the result
Example
Multiply:           0.3 x 0.12

Ans:              3          Multiply as normal
x   12
36

0.3      1 decimal place
0.12     2 decimal places

So, we need 3 decimal places for the result.

Thus, the answer is 0.036          3 decimal places
You Try!!!

Multiply:

1.   0.13 × 12.1

2.   4.536 × 100
Method: Dividing by Whole #

1. Place decimal point directly above
2. Divide as normal
Example
Divide:
33.6  6
Ans:
5 .6
6 33 .6
30
36
36
0
You Try!!!
Divide:

2.3  5
Dividing by Decimal

1. Convert denominator (divisor) to whole
number by moving decimal point to right
2. Move the numerator (+ result) to the right
the same number of decimal points
3. Divide as normal
Example
Divide:
0.75 1.5
Ans:
0.5
15 7.5
75
0
You Try!!!
Divide:

5.12 1.6
Section 8.6

Percents
Def: Percents
Percent (symbolized as %) means “parts
per hundred.”

Ex:

14 out of 100 students = 14% of students.
Method: Percents to decimals

• Percent  Decimal: Move decimal point 2
places left + drop the %-symbol.

• Decimal  Percent: Move decimal point 2
places right + add the %-symbol.
Example
Convert 27.5% to a decimal.

Ans:

27.5% becomes 0.275
You Try!!!

1.   Convert 1.1 to a percentage.

2.   Write 2.6% as a decimal.
Example
211
Write        as a percent.
500

Ans: First, we convert to a decimal:

211                         211
 0.422          So,        42.2%
500                         500
Section 8.7

Solving Percent Problems using
Equations
Property: Percents
amount = percent x base

Ex:        3 is 75% of 4

(3) = (0.75)x(4)
You Try!!!
1.   What is 25% of 40?

2.   10 is 25% of what number?

3.   36 is what percent of 90?
You Try!!!
The new 8-mile nature trail is 125% of the
length of the original trail. How long was
the original trail?
Complete IC11

• Spend the rest of the class completing the
worksheet In-Class Exercises: Set 11.
• Feel free to work together in groups.
• Feel free to ask me questions.
• Feel free to have me check your work.
• Feel free to have me do example
problems on the board.
To Do for Next Week

• Read Sections 8.2-8.3, 8.6-8.7 in the book
• Check out Sections 8.8, 9.1-9.2 in the
book
• MyMathLab Homework Set # 11
• Work on Exam 3

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