Ratios, Rates & Proportions Key Definitions Ratio — comparison of two quantities (a:b or a/b) Rate — ratio with different units (miles/hour, $/item) Proportion — equation stating two ratios are equal a/b = c/d → cross multiply: ad = bc Unit Conversion Multiply by conversion factors where units cancel Example: 60 mph × (5280 ft/mi) × (1 hr/3600 sec) = 88 ft/sec SAT Tips Set up proportions carefully — keep units consistent For "per" problems, identify the rate and multiply/divide Watch for part-to-part vs part-to-whole ratios