VIEWS: 4 PAGES: 5 CATEGORY: Personal Finance POSTED ON: 2/12/2010 Public Domain
POTD Ratio and Proportion • If 3 apples cost $4, how much will 6 • To find ratios and rates apples cost? • To solve proportions Definitions • A ratio is a comparison of two numbers. Example • The ratio of a to b can be written three ways: a • Which is the best a to b a :b buy? b • If a and b have different units, the ratio is • Find the unit called a rate. rates to support your answer. • A unit rate has demonimator 1. • We use rates to compare items for a “better buy” and for other comparisons in general. 1 More with Unit rates Conversions • The formula “d=rt” requires a unit rate for r. • Conversion factors are another place • In 2004, Lance Armonstrong won the Tour that unit rates are used. de France. • Multiplying by conversion factors to • He completed the 3391 km course in 83.6 hours. change one rate to another is called “Dimensional Analysis.” • Write an equation that represents this. • Find the unit rate. • We will do this with speeds. • Use this to predict how long it would take for him to travel 185 km. Examples Examples • A snail travels 3 feet per day. • A car travels 60 miles per hour. • How many inches per minute is this? • How many feet per second is this? • Another snail travels 0.5 feet per hour. • Another car travels 44 feet per second. • How many inches per day is this? • How many miles per hour is this? 2 Examples Proportions • 5 gorbles is equal to 1 zorble. • 3 zorbles are equal to 2 borbles. • A proportion is an Solve: equation that states two ratios are equal. x 5 • You have 20 gorbles. = • We solve this with 9 6 • How many borbles is this equal to? cross multiplication. – We could also • You have 8 borbles. multiply both sides by the LCD. • How many gorbles is this equal to? Examples Example Solve: Solve: • A box of cereal weighs 354 grams. x 9 x !11 • It contains 20 grams of fat. = = 3 8 5 3 • A serving size is 55 grams of cereal. • How many grams of fat are in one serving? 3 Multi-step proportions Literal Equations • Solve: • A literal equation is an equation that contains two or more variables. x+4 x!2 3 = 5 = – Formulas are literal equations. 5 7 w+6 w!4 • You can solve for a variable in a literal equation by using the inverse operation steps. Examples Transforming Equations Solve for w: Solve for h: Solve for x: Solve for y: P = 2l + 2w 1 2x ! 3y = !6 2x ! 3y = !6 A = bh 2 4 Most Common Example Ever Ratio and Proportion • To find ratios and rates • To solve proportions • Homework: – Starts on page 145 – See assignment sheet 5