9.1 & 9.2: Percentages, Fractions, and Decimals Essential Question: When and why do I use proportional comparisons?
Review Write each fraction as a decimal Write each decimal as a fraction __ 9 10 __
What is a percent? A percent is a ratio that compares a number to 100. The symbol % is used to show a percent.
Think-Pair-Share Is it possible to have a percent over 100? Is it possible to have a decimal in a percentage?
Using a Grid to Model Percents Model 17% on a 10 by 10 grid Model 26% on a 10 by 10 grid
Percent FractionFraction Percent Step 1: Write the percent as the numerator and 100 as the denominator Step 2: If necessary, multiply the fraction to “get rid of” all decimals in the numerator. Step 3: If necessary, simplify the fraction. If the denominator is a factor of 100, multiply to find an equivalent fraction with a denominator of 100 If the denominator is NOT a factor of 100, divide the numerator by the denominator to change to a decimal. Then, multiply by 100.
Percent DecimalDecimal Percent Step 1: Divide the percent by 100, which is the same as moving the decimal TWO places to the left Step 1: Multiply the decimal by 100, which is the same as moving the decimal TWO places to the right.
Fraction DecimalDecimal Fraction Step 1: Divide the numerator by the denominator. Step 1: Read the decimal. The place value of the last decimal tells you the denominator of the fraction.
IS OVER OF = % OVER 100
Example Problems Find 46% of 50 (Hint: You can rephrase the question as “What is 46% of 50?”) Find 75% of 120 (Hint: You can rephrase the question as “What is 46% of 50?”)
Word Problems A jacket is on sale for 25% off. The original price of the jacket was $45. How much would the jacket cost after the discount? At a cat show, 60% of the cats had long hair. There were 168 cats in the show. How many cats had long hair? The budget for a café includes $3,000 for new kitchen equipment. The chef spent 3% of that money for new aprons. How much money was spent on aprons?