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Unit 2

Unit 2. Percent. Unit 2.1. Writing Decimals and Fractions as Percents. What is percent?. It means Per – 100 (like 100 cents in a dollar) When we say percent, we mean, how many equal parts of 100. For example, “One percent” (written 1%) means 1 of 100 equal parts. (1/100)

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Unit 2

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  1. Unit 2 Percent

  2. Unit 2.1 Writing Decimals and Fractions as Percents

  3. What is percent? • It means Per – 100 (like 100 cents in a dollar) • When we say percent, we mean, how many equal parts of 100. • For example, “One percent” (written 1%) means 1 of 100 equal parts. (1/100) • “Fifty percent” (written 50%) means 50 out of 100. (50/100)

  4. What decimal is 1/100? So 1/100 is the same as 0.01 is the same as 1% What decimal is 50/100? So 50/100 is the same as 0.50 is the same as 50%

  5. Writing a decimal as a percent • To write a decimal as a percent, move the decimal point two places to the right and attach a percent sign (%). = 75% 0.75 .

  6. Examples • Write the following decimals as percents: • .35 • .42 • .58 35% 42% 58%

  7. More Examples • Try writing these decimals as percents: • .011 • .3467 • 2.6 • 0.008 1.1% 34.67% 260% .8%

  8. Writing a fraction as a percent • There are multiple ways to write a fraction as a percent. • Method 1: Convert the denominator of the fraction to 100, then the percent is the numerator. • Method 2: Multiply the fraction by 100%, then simplify. • Method 3: Change the fraction to a decimal, and then write it as a percent.

  9. Method 1: Convert the denominator of the fraction to 100, then the percent is the numerator. 40 100 8 20 5 5 = = 40%

  10. Method 2: Multiply the fraction by 100%, then simplify. 4 5 4 5 400% 5 = = =  100% 80% 3 8 = 37.5%

  11. Method 3: Change the fraction a decimal, and then write it as a percent. 1 2 = 0.5 = 50%

  12. Examples • Write the following fractions as percents. • 7/20 • 11/50 • 22/25 • 2/5 • 5/8 35% 22% 88% 40% 62.5%

  13. Writing a percent as a decimal. • To write a percent as a decimal, move the decimal point two places to the left and drop the percent sign (%). .75 . 75% =

  14. Examples • Change the following percents to decimals: • 35% • 50% • 325% • 37½% 0.35 0.5 3.25 0.375

  15. More Examples • Try writing these percents as decimals. • ½% • ¾% • ¼% 0.5% = .005 0.75% = .0075 0.25% = .0025

  16. Homework 1 • Find a newspaper article that mentions at least three different percentages. • Bring the article to class. • Hi-light the percentages. • Write in complete sentences what these percents are used for. • Change the percentages to decimals. • Change the percentages to fractions.

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