Download Chapter 7 Notes (Percent)

Name: ________________Chapter 7 Percent Test Date:____
Chapter 7: Percent
Vocabulary:
percent___________________________________________________
_________________________________________________________
discount___________________________________________________
_________________________________________________________
principal___________________________________________________
________________________________________________________
interest___________________________________________________
_________________________________________________________
simple interest______________________________________________
_________________________________________________________
Lesson 7.1 Understanding Percent
Warm-Up: Solve each proportion.
1
n
3
n
1.
=
2.
=
5 100
10 100
3.
3
n
=
4 100
4.
n
85
=
20
100
A percent is a ratio in which the first term is compared to 100.
Examples on the front of workbook page 76.
1
Lesson 7.2 Fractions, Decimals, and Percents
_________________________________________________
Warm –Up:
1. Shade two squares, and then write the fraction of the shaded area in
simplest form.
2. Shade two squares, and then write the fraction of the shaded area in
simplest form.
_________________________________________________________
Percent means per 100.
Example 1: Write 60% as a fraction and decimal.
60% =
----- =
0.60
Example 2: Write 0.38 as a fraction and percent.
0.38 =
----- =
___%
3
as a percent.
8
One way:
Use a proportion.
3
n
=
8
100
Example 3: Write
A.
B.
Another way: Divide numerator by denominator
3÷8=
Example 4: Write 0.5% as a fraction and decimal.
0.5% =
----- =
____
Example 5: Write .05 as a percent and fraction.
.05
=
----- =
____%
Example 6: Write 0.525 as a fraction and percent.
0.525 =
----- =
___%
Examples on the front of workbook page 77.
2
Lesson 7.3 Writing to Explain
When you write to explain, it is important that you describe each step in the
solution clearly.
Tips for Writing Good Explanations:
 Break explanations into parts to make them easy to follow.
 Use specific numbers for examples to explain why something works or
does not work.
 Give alternate explanations if appropriate.
Examples on the front of workbook page 78.
Lesson 7.4 Mental Math: Finding Percent of a Number
Warm Up: Write each percent as a fraction.
1. 25% = _____ 2. 50% = _____ 3. 75% = _____
4. 10% = _____
Benchmark Fractions: (Memorize these…it will be helpful.)
Percent
10%
20%
Fraction
1
10
1
5
25% 33 1 %
3
1
1
4
3
40%
50%
60%
2
5
1
2
3
5
2
%
3
2
3
66
75%
80%
3
4
4
5
**You can use the fraction equivalents to find a percent of a whole number
mentally, especially when the denominator easily divides into the whole
number.
Example 1:
4
A.
Strategy One: Think 80% is .
5
4
x 40 = 32
5
B.
Strategy Two:
3
Think: 80% is 8 x 10%.
10% of 40 is 4,
8 x 4 = 32
Examples on the front of workbook page 79.
Lesson 7.5 Estimating with Percents
Warm Up: Multiply.
1
1.
x 18 = ________
2
3.
5
x 66 = ________
6
2.
3
x 40 = ________
4
4.
2
x 100 = ________
5
Two ways to estimate are:
A.____________________
B.____________________
Example 1: Estimate 34% of 600,000 using compatible numbers.
Example 2: Estimate 9% of 735,617 using compatible numbers and rounding.
Examples on the front of workbook page 80.
Lesson 7.6 Finding the Percent of a Number
4
Warm Up: Write each percent as a decimal.
1. 10% = _____
2. 32.5% = _____ 3. 6% = _____
4. 125%= _____
Percents can be converted to fractions and/or decimals.
Example 1: Write the percent as a decimal.
21% of 346
Example 2: Write a proportion.
part =
percent value
whole
100
Examples on the front of workbook page 81.
Lesson 7.7 Solve a Simpler Problem
Examples on the front of workbook page 82.
Lesson 7.8 Sales Tax and Discount
5
Warm Up: Find each value.
1. 5% of 50
2. 25% of 84
3. 20% of 15
4. 10% of 18
A. How do you calculate sales tax?
To calculate sales tax
1. Convert the percent to a decimal.
2. Multiply the decimal (% sales tax) by the subtotal
of the item. Round to the nearest hundredth
(remember that $$$ has two decimals places to
the right of the decimal…tenths, hundredths).
3. Add the sales tax to the subtotal.
4. Then you will have the total cost of the bill.
Total cost = subtotal + sales tax
Example: Find the total cost of a pair of jeans that cost
$29.56. The sales tax equals 6%.
1.
2.
3.
4.
B. How to calculate a discount? (Do you want to save $$$?)
6
1. Convert the percent of the discount to a decimal.
2. Multiply the decimal by the original price. Round to the nearest
hundredth. This is the amount of $ you save.
3. Subtract the discount from the original (sticker/tag) price. This
will give you the sale price.
4. Then you have the sale price of the discounted item.
** Now follow the rules for finding the sales tax of the item you are
purchasing.
Example: Now the jeans that originally cost $29.56 are on
sale for 20% off.
Calculate the discount:
1.
2.
3.
4.
Now calculate the sales tax of the discounted pair of jeans:
1.
2.
3.
4.
Examples on the front of workbook page 83.
Lesson 7.9 Percent of Increase and Decrease
7
Warm Up:
1.
3.
Write each decimal as a percent.
0.19
2.
0.125
1.10
4.
0.0325
You can use percents to show a change of increase or decrease:
A.
Read the problem to identify if you are going to have a percentage
increase or decrease.
B.
To show an amount of increase:
1.
Subtract to find the amount of increase.
2.
Write and solve a proportion to find the percent
of increase.
percent change = increase amount
100
original amount
Example: Last year the book for required reading cost $5.00. This year
the same paperback book costs $6.00. Find the percentage
increase using the percentage increase formula.
C.
To show an amount of decrease:
1. Subtract to find the amount of decrease.
2. Write and solve a proportion to find the percent decrease.
percent change
=
decrease amount
100
original amount
Example:
The Windsor School library purchased 200 new books in 2002.
In 2003, the school library purchased only 180 new books.
8
Examples on the front of workbook page 84.
Lesson 7.10 Simple Interest
Warm Up: Multiply.
1.
30 x 0.2
_____
2.
6 x 0.35 _____
3.
4.
0.035 x 80 _____
420 x 0.5
_____
principal-An amount of money borrowed or loaned.
interest-A charge for the use of money, paid by the borrower to
the lender.
simple interest-Interest paid only on the principle, found by
taking the product of the principle, rate, and time.
Simple interest = principal • rate • time
I = p • r •t
Step 1: Write the formula
Step 2: Substitute the given information
Step 3: Solve.
Ask yourself if your answer makes sense.
Examples on the front of workbook page 85.
Are you ready for the Chapter 7 Test?
Three things I really understand are:
9
1.
2.
3.
Three things I still need more practice on are:
1.
2.
3.
10