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3-4 Ratios and Proportions (p. 142)

3-4 Ratios and Proportions (p. 142). Algebra 1 Prentice Hall, 2007. Set up your Flip Book!. fold line. Objectives. You will… learn the difference between a RATIO and a RATE . find a UNIT RATE . use UNIT ANALYSIS to convert from one unit to another.

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3-4 Ratios and Proportions (p. 142)

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  1. 3-4 Ratios and Proportions(p. 142) Algebra 1 Prentice Hall, 2007

  2. Set up your Flip Book! fold line

  3. Objectives You will… • learn the difference between a RATIO and a RATE. • find a UNIT RATE. • use UNIT ANALYSIS to convert from one unit to another. • Use the CROSS PRODUCTS PROPERTY to solve a PROPORTION.

  4. Ratios (top flap) • A ratio is a comparison of 2 numbers by division. Ex. 1 The ratio of girls to boys in this class is ____:____.

  5. Ratios (bottom flap) • NOTE: Order matters! Ex. 2 The freshmen football team’s Win/Loss record is ____:____.

  6. Rates (top half of top flap ) • If the 2 quantities in a ratio are in different units, the ratio is called a rate. Ex. 1 “mpg”  Ex. 2 “cost per ounce” 

  7. Rates (rest of top flap) • If a rate has a denominator of 1, it is called a unit rate. (It means you’re comparing “per 1 of something”!) Ex. 3 There are 140 calories in a handful of 50 goldfish. How many calories is just one goldfish? (Think: ) That’s Now divide top by bottom!

  8. Rates (bottom flap) • Unit analysis is a process of changing from 1 unit to another and cross reducing along the way: • Start with what you’re given on the top of the 1st fraction and put a 1 under it. • Multiply by as many comparative ratios as it takes to end with the unit you want on top of the last fraction. • Cancel out all other units along the way. Ex. 1 How many cups are in a 5-gallon container of water?

  9. Rates • Another example… just watch! Ex. 4 A cheetah was clocked at 70 mph. What is his speed in feet per second?

  10. Proportions (top flap) • A proportion is an equation that shows that 2 ratios are equal. Ex. 1 Say: “3 is to 12 as 8 is to 32” Ex. 2 Can you write a proportion with these 2 ratios?

  11. Proportions (bottom flap) • To solve a proportion, use the “Cross-Products Property” (AKA the “heart method”!)

  12. Assignment • 3-4 p. 146: evens (2-48, except 10, 12, 14); add 45, 52, 70, 72

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