PRE-ALGEBRA. Lesson 6-4 Warm-Up PRE-ALGEBRA What is “percent”? How do you write a percent as a...
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Transcript of PRE-ALGEBRA. Lesson 6-4 Warm-Up PRE-ALGEBRA What is “percent”? How do you write a percent as a...
PRE-ALGEBRA
PRE-ALGEBRA
Lesson 6-4 Warm-Up
PRE-ALGEBRA
What is “percent”?
How do you write a percent as a fraction or a decimal?
percent: a ratio that compares a number to 100
To write a percent as a fraction, make the numerator the percent and the denominator 100 (“out of 100”). Then, simplify the fraction. To write a percent as a decimal: turn it into a fraction first (then you can turn the fraction into a decimal by dividing) or simply move the decimal two places to the left.
Example:The following model shows 41 out of 100 squares shaded, or 41% of the big square shaded.
Example:Write 125% each percent as a fraction and a decimal.
Write as a fraction with a denominator of 100.
Then, simplify the fraction.
Write the improper fraction as a mixed number.
Divide the numerator by the denominator to change a fraction into a decimal.
Fractions, Decimals, and Percents (6-4)
125100
2525
= 54
54
14= 1
5 4 = 1.25
PRE-ALGEBRA
Write each percent as a fraction or a mixed number.
a. 30%
b. 175%
Write as a fraction with a denominator of 100.30
100
Simplify.3
10
Write as a fraction with a denominator of 100.175100
1 Write as a mixed number.34
Simplify.74
Fractions, Decimals, and PercentsLESSON 6-4
Additional Examples
PRE-ALGEBRA
Express 7.3% as a decimal.
= 0.073
7.3% = Write as a fraction with a denominator of 100.7.3100
= 007.3 Divide by moving the decimal point left two places.You may need to write one or more zeros.
Fractions, Decimals, and PercentsLESSON 6-4
Additional Examples
PRE-ALGEBRA
Fractions, Decimals, and Percents (6-4)
(7-1)
How do you write a fraction as a percent?
To write a fraction as a percent, find an equal fraction with a denominator of 100 (if the denominator is 100, the numerator will always be the percent, since percent means “out of 100”) or make a proportion and use cross products.Example: According to the school cafeteria, 6 out of 25 students bring their lunch to school. What percent of the students bring their lunches to school?
Method 1: Proportion
# %
Known (Part) 6 x
Unknown (Whole) 25 100
= Proportion .6
25x
100
25 • x = 6 • 100 Cross products are equal.
25x = 600 Simplify.
= Divide both sides by 25. .25x25
60025
x = 24 Simplify.
24% of the students bring their lunches..
1
1
24
1
PRE-ALGEBRA
How do you write a fraction as a percent?
Method 2: Equal Fractions
= Write an equal fraction with a denominator of 100 (since percents have 100 in the denominator.
625 100
= Multiply the numerator by the same number that you multiply the denominator by to find the equivalent fraction with a denominator of 100.
625
24100
4
4
24% of the students bring their lunches..
Fractions, Decimals, and Percents (6-4)
PRE-ALGEBRA
Write as a percent.7
20
= Find the fraction with denominator 100
that is equal to .
720
35100
5
5
720
720 = Write a proportion. Percents have
100 in the denominator.
p100
720 = = 35% Write using a percent symbol.35
100
Fractions, Decimals, and PercentsLESSON 6-4
Additional Examples
PRE-ALGEBRA
Four out of seven members of the chess club won a game at the district tournament. What percent of the chess club members won a game?
0.5714 Divide the numerator by the denominator.
57.14% Write as a percent.
About 57% of the chess club members won a game.
Write a fraction.47
Fractions, Decimals, and PercentsLESSON 6-4
Additional Examples
PRE-ALGEBRA
“Fractions, Decimals, and Percents” (6-4)
(7-1)How do you write a decimal as a percent?
To write a decimal as a percent, write the decimal as a fraction and change the fraction into a percent using proportions or equal fractions or move the decimal two places to the right.
Method 1: Change the decimal to a fraction
Example: Write 0.076 as a percent.
Method 2: Move the decimal 2 places to the right.
0.076 = Write the decimal as a fraction the way you read it.
761000
0.076 = 7.6%
= Divide the numerator by the same number that you divide the denominator by to find the equivalent fraction with a denominator of 100.
761000
7.6100
10
10
0. 0 7 6 Jump the decimal two places to the right.
= 7 . 6 %
PRE-ALGEBRA
Write each decimal as a percent.
a. 0.16
b. 0.03
0.16 = 16100 Write the decimal as a fraction.
= 16% Write as a percent.
0.03 = 3100 Write the decimal as a fraction.
= 3% Write as a percent.
Fractions, Decimals, and PercentsLESSON 6-4
Additional Examples
PRE-ALGEBRA
Express 0.412 as a percent.
Method 1 Rewrite as a fraction.
= 41.2%
Method 2 Move the decimal point.
0.412 = 41.2%
0.412 = 4121,000
= 412 ÷ 101,000 ÷ 10
= 41.2100
Fractions, Decimals, and PercentsLESSON 6-4
Additional Examples
PRE-ALGEBRA
Write each percent as a fraction or mixed number, and as a decimal.
1. 325% 2. 1.1%
Write each as a percent.
3. 2.01 4.
5. Six out of fifteen students own skateboards. What percent of students own skateboards?
134
, or 3 ; 3.2514
111,000
; or 0.011
201%
35
60%
40%
Lesson Quiz
Fractions, Decimals, and PercentsLESSON 6-4