confidential1 today we will review “percents”. confidential2 let’s warm up: 1) ¾ x ¼ =2) 3/5...
TRANSCRIPT
CONFIDENTIAL 3
Modeling Percents A percent (%) is a ratio that compares a number to 100
75% = 75 out of 100 Use a 10 x 10 grid to model percents Example: Model 18%
18% means 18 out of 100 So, shade 18 out of the 100 squares
CONFIDENTIAL 5
Modeling Percents Identify a percent that is modeled
There are 40 out of 100 squares shaded So, the model shows 40%
CONFIDENTIAL 7
Percents & Fractions All percents can be written as fractions in simplest form
To write a percent as a fraction, Write the percent as a fraction with a denominator as 100 Then simplify
Write 50% as a fraction in simplest form 50% means 50 out of 100
2
1
100
50
100
50%50
2
1
or
Write the percent as a fraction with a denominator of 100
Simplify. Divide the numerator and the denominator by the
GCF, 50
CONFIDENTIAL 8
Percents & Fractions Write 125% as a fraction in simplest form
125% means 125 for every 100
4
11
100
521
100
125%125
4
1
or
CONFIDENTIAL 10
Percents & Fractions Write a Fraction as a Percent
Write 9/10 as a percent
90% toequivalent is 10
9 So,
Simplifyn 90
10by sideeach Divide 10
10
100
900
Multiply10n 900
products cross then Write x 10 100 x 9
proportion a upSet 100100
9
n
n
CONFIDENTIAL 12
Percents & Decimals Percents can be written as a decimal To write a percent as a decimal
Rewrite the percent as a fraction with a denominator of 100 Then write the fraction as a decimal
Write 56% as a decimal
Shortcut: Move the decimal point two places to the left, which is the same as dividing by 100
decimal a asfraction the Write0.56
100 ofr denominato aith fraction w a aspercent theRewrite 100
56%56
CONFIDENTIAL 14
Percents & Decimals To write a decimal as a percent
Write the decimal as a fraction whose denominator is 100 Then write the fraction as a percent
Write 0.38 as a percent 0.38 = 38/100 Write the decimal as a fraction
= 38% Write the fraction as a percent Shortcut: Move the decimal place two places to the right, which is
same as multiplying by 100
CONFIDENTIAL 16
Percent of a Number To find the percent of a number
Write the percent as a fraction and then multiply or Write the percent as a decimal and then multiply
Find 5% of 300 Method 1: Write the percent as a fraction
15. is 300 of 5% So,
15or 30020
1300
20
120
1or
100
5%5
of
CONFIDENTIAL 17
Percent of a Number Method 2: Write the percent as a decimal
Use a model to check the answer.
The model confirms that 5% of 300 is 15
15. is 300 of 5% So,
15or 30005.0300 05.0
0.05or 100
5%5
of
0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%
0 30 60 90 120 150 180 210 240 270 300
CONFIDENTIAL 19
Estimating with Percents Sometimes when finding the percent of a number, an exact number is not
needed So, you can estimate Commonly used Percents and their Fraction equivalents
3
1%
3
133
5
1%20
2
1%50
5
4%80
4
1%25
10
3%30
5
3%60
10
9%90
4
3%75
3
2%
3
266
5
2%40
10
7%70 1%100
CONFIDENTIAL 20
Estimating with Percents Estimate 52% of 298
52% is close to 50% or ½ Round 298 to 300 ½ of 300 is 150 So, 52% of 298 is about 150
CONFIDENTIAL 25
Assessment
3. Write 97% as a fraction in simplest form.
4. Write 3/5 as a percent.
5. Write 32% as a decimal.
6. Write 0.47 as a percent.
7. Find 55% of 160.
8. Estimate 48% of $76
9. Ian used 35% of his allowance to buy a book. If Ian received $20 for his allowance, how much did he use to buy the book?
10. Melissa bought a sweatshirt that originally cost $30. If the sweatshirt was on sale for 25% off, what was the discount?