Presentation on theme: "3-4 Ratios and Proportions (p. 142)"— Presentation transcript:
13-4 Ratios and Proportions (p. 142) Algebra 1Prentice Hall, 2007
2Set up your Flip Book!fold lineRatiosRatesProportions
3Objectives 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.
4Ratios (top flap) A ratio is a comparison of 2 numbers by division. Ex. 1 The ratio of girls to boys in thisclass is ____:____.
5Ratios (bottom flap) NOTE: Order matters! Ex. 2 The freshmen football team’sWin/Loss record is ____:____.
6Rates (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”
7Rates (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 of50 goldfish. How many calories is justone goldfish? (Think: )That’sNow divide top by bottom!
8Rates (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-galloncontainer of water?
9Rates Another example… just watch! Ex. 4 A cheetah was clocked at 70 mph.What is his speed in feet per second?
10Proportions (top flap) A proportion is an equation that shows that 2 ratios are equal.Ex Say: “3 is to 12 as 8 is to 32”Ex. 2 Can you write a proportion withthese 2 ratios?
11Proportions (bottom flap) To solve a proportion, use the “Cross-Products Property” (AKA the “heart method”!)Ex. 3 Solve:Ex. 4 Solve: