7-7 percents warm up warm up lesson presentation lesson presentation problem of the day problem of...
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7-7 Percents
Warm UpWrite each fraction as a decimal.
1. 2.
Write each decimal as a fraction.
3. 0.375 4. 0.05
0.75 0.934__ 9
10 __
38__ 1
20 __
7-7 Percents
Problem of the Day
Wally wanted to change the scale of a drawing from 1 in. = 2 ft to 1 in. = 10 ft. The scale height of a building in the first drawing is 25 in. How high is the building in the new drawing?5 in.
7-7 Percents
Most states charge sales tax on items you purchase. Sales tax is a percent of the item’s price. A percent is a ratio of a number to 100.
You can remember that percent means “per hundred.” For example, 8% means “8 per hundred,” or “8 out of 100.”
7-7 Percents
If a sales tax rate is 8%, the following statements are true:
• For every $1.00 you spend, you pay $0.08 in sales tax.
• For every $10.00 you spend, you pay $0.80 in sales tax.
• For every $100 you spend, you pay $8 in sales tax.
Because percent means “per hundred,” 100% means “100 out of 100.” This is why 100% is often used to mean “all” or “the whole thing.”
7-7 Percents
Additional Example 1: Modeling Percent
Use a 10-by-10-square grid to model 17%.
A 10-by-10 square grid has 100 squares.
17% means “17 out of 100”
or .
Shade 17 squares out of 100 squares.
17100
___
7-7 Percents
Check It Out: Example 1
Use a 10-by-10-square grid to model 26%.
A 10-by-10 square grid has 100 squares.
26% means “26 out of 100”
or .
Shade 26 squares out of 100 squares.
26100
___
7-7 Percents
Additional Example 2: Writing Percents as Fractions
Write 35% as a fraction in simplest form.
Write the percent as a fraction with a denominator of 100.
Write the fraction in simplest form.
35% = 35100
___
35 ÷ 5100 ÷ 5
_______ = 720 __
Written as a fraction, 35% is . 720 __
7-7 Percents
Check It Out: Example 2
Write 65% as a fraction in simplest form.
Write the percent as a fraction with a denominator of 100.
Write the fraction in simplest form.
65% = 65100
___
65 ÷ 5100 ÷ 5
_______ = 1320
__
Written as a fraction, 65% is . 1320 __
7-7 Percents
Additional Example 3: Life Science Application
Janell has 20% body fat. Write 20% as a fraction in simplest form.
Write the percent as a fraction with a denominator of 100.
Write the fraction in simplest form.
20% = 20100
___
20 ÷ 20100 ÷ 20
_______ = 1 5 __
Written as a fraction, 20% is . 1 5 __
7-7 Percents
Check It Out: Example 3
Timmy has 14% body fat. Write 14% as a fraction in simplest form .
Write the percent as a fraction with a denominator of 100.
Write the fraction in simplest form.
14% = 14100
___
14 ÷ 2100 ÷ 2
_______ = 750
__
Written as a fraction, 14% is . 750 __
7-7 Percents
Additional Example 4: Writing Percents as Decimals
Write 56% as a decimal.
Write the percent as a fraction with a denominator of 100.
Write the fraction as a decimal.
56% = 56100
___
Written as a decimal, 56% is 0.56.
100 56.000.56
–500 600
–6000
To divide by 100, move the decimal point two places to the left. 56 ÷ 100 = 0.56
Remember!
7-7 Percents
Check It Out: Example 4
Write 32% as a decimal.
Write the percent as a fraction with a denominator of 100.
Write the fraction as a decimal.
32% = 32100
___
Written as a decimal, 32% is 0.32.
100 32.000.32
–300 200
–2000
7-7 Percents
Additional Example 5: Application
Water made up 85% of the fluids that Kirk drank yesterday. Write 85% as a decimal.
Write the percent as a fraction with a denominator of 100.
Write the fraction as a decimal.
85% = 85100
___
85 ÷ 100 = 0.85
Written as a decimal, 85% is 0.85.
7-7 Percents
Check It Out: Example 5
Water made up 95% of the fluids that Lisa drank yesterday. Write 95% as a decimal.
Write the percent as a fraction with a denominator of 100.
Write the fraction as a decimal.
95% = 95100
___
95 ÷ 100 = 0.95
Written as a decimal, 95% is 0.95.
7-7 Percents
Lesson Quiz
Write each percent as a fraction in simplest form.
1. 52% 2. 29%
Write each percent as a decimal.
3. 17% 4. 86%
5. A store clerk has an 8% sales increase. Write
the increase as a fraction in simplest form and as
a decimal.
, 0.08
1325 __ 29
100 ___
0.17 0.86
225 __
7-7 Percents
1. Which of the following represents 15% as a fraction in simplest form?
A. B.
C. D.
Lesson Quiz for Student Response Systems
7-7 Percents
2. Which of the following represents 79% as a fraction in simplest form?
A. B.
C. D.
Lesson Quiz for Student Response Systems
7-7 Percents
3. Which of the following represents 26% as a decimal?
A. 2.6 B. 0.026
C. 0.26 D. 0.0026
Lesson Quiz for Student Response Systems
7-7 Percents
4. Which of the following represents 71% as a decimal?
A. 71 B. 0.71
C. 7.1 D. 0.071
Lesson Quiz for Student Response Systems