Proportional Ratios

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What is a proportional ratio?

Back

A proportional ratio is a relationship between two quantities where the ratio of one quantity to another remains constant. For example, if the ratio of boys to girls in a class is 2:3, it means for every 2 boys, there are 3 girls.

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How do you determine if two ratios are proportional?

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Two ratios are proportional if their cross products are equal. For example, for the ratios a:b and c:d, they are proportional if a*d = b*c.

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What is the formula for finding a missing value in a proportional ratio?

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The formula is: (a/b) = (c/d), where a and b are the known values, and c is the known value while d is the missing value. You can solve for d by rearranging the formula.

Front

Give an example of a real-life situation that involves proportional ratios.

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A real-life example is cooking. If a recipe requires 2 cups of flour for every 3 cups of sugar, the ratio of flour to sugar is 2:3. If you want to use 4 cups of flour, you would need 6 cups of sugar to maintain the same ratio.

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What is the relationship between proportional ratios and scale factors?

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Proportional ratios are used to determine scale factors in similar figures. If two shapes are similar, the ratio of their corresponding sides is constant, which is the scale factor.

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What is a unit rate?

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A unit rate is a ratio that compares a quantity to one unit of another quantity. For example, if a car travels 300 miles in 5 hours, the unit rate is 60 miles per hour.

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How can you use proportional ratios to solve problems involving percentages?

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You can set up a proportion to find the percentage. For example, if you want to find what percentage 20 is of 80, you can set up the proportion 20/x = 80/100 and solve for x.

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What is the difference between direct and inverse proportions?

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In direct proportion, as one quantity increases, the other also increases (e.g., distance and time at constant speed). In inverse proportion, as one quantity increases, the other decreases (e.g., speed and travel time).

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How do you apply proportional ratios in financial literacy?

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Proportional ratios can help in budgeting. For example, if you earn $500 and want to save 20%, you can set up the ratio 20/100 = x/500 to find out how much to save.

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What is a ratio?

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A ratio is a comparison of two quantities by division. It shows how many times one value contains or is contained within the other.