Ratios and Rates
A ratio compares two quantities. A rate compares quantities with different units.
Core Concept
A RATIO compares two numbers: 3 cats to 5 dogs is 3:5 or 3/5. EQUIVALENT RATIOS are like equivalent fractions: 3:5 = 6:10 = 9:15. A RATE uses different units: 60 miles per hour, $3 per pound. A UNIT RATE has 1 in the denominator: $3/pound means $3 for each pound. To find unit rate, divide: 120 miles in 2 hours = 60 mph. Ratios are everywhere: recipes, maps, sports stats.
Examples
Recipe: 2 cups flour to 1 cup sugar = 2:1. Speed: 150 miles in 3 hours = 50 mph. Price: $12 for 4 = $3 each.
If there are 8 boys and 12 girls, what is the ratio?
Going Deeper
Unit rates help you compare prices and find the best deal.
Recipe Ratios
Find a recipe. Write every ratio in it. Then double the recipe by scaling each ratio.
Best Deal Challenge
Compare unit prices of 3 different sizes of the same product. Which is the best value?
What is the unit rate of 240 miles in 4 hours?
3:5 = 9:?
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