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Solving Proportions

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Warm-Up 1. 1. Uptown Pizza sells medium pizzas for $7 each but charges $3 delivery fee per order. Is the cost of an order proportional to the number of pizzas ordered? 2. At the beginning of the school year, Isabel had $120 in the bank. Each week, she deposits another $20. Is her account balance proportional to the number of weeks since she started school? 3. Simplify: 12 missed days out of 180 days 4. Simplify: 1 cup of vinegar in 8 pints of water 5. Better buy: A 17-ounce box of cereal for $4.89 or a 21-ounce box for $5.69

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Warm-Up 1. 1. Uptown Pizza sells medium pizzas for $7 each but charges $3 delivery fee per order. Is the cost of an order proportional to the number of pizzas ordered? Non Proportional

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Warm-Up 2. At the beginning of the school year, Isabel had $120 in the bank. Each week, she deposits another $20. Is her account balance proportional to the number of weeks since she started school? Non Proportional

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Warm-Up 3. Simplify: 12 missed days out of 180 days 1 : 15

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Warm-Up 4. Simplify: 1 cup of vinegar in 8 pints of water 1 : 16

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Warm-Up 5. Better buy: A 17-ounce box of cereal for $4.89 or a 21-ounce box for $5.69 21 ounce box for $5.69

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Proportion A proportion is an equation stating that two ratios or rates are equivalent. Una proporción es una ecuación que establece que dos razones o tasas son equivalentes. Consider the following proportion: 6 3 8 * 3 = 24 8 46 * 4 = 24 = Record the definition in your math journal on page P.

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Cross Products The products 8 * 3 and 6 * 4 are called the cross products of this proportion. The cross products of any proportion are equal. Los productos 8 * 3 y 6 * 4 se llaman los productos cruzados de esta proporción. Los productos cruzados de cualquier proporción son iguales. You can use cross products to solve proportions in which one of the quantities is not known.

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Write and Solve a Proportion After 2 hours, the water in a heated pool had risen 7°C. Write and solve a proportion to find the amount of time it will take at this rate for the temperature to rise an additional 14°C. Write a proportion. Let t represent the time in hours. 7 14 2 t = Temp Time

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To find the unknown, we must use cross products. 7 14 2 t 7 * t = 2 * 14 7t = 28 7 7 t = 4 =

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Example Problems Solve the proportion. x9 410 =

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Solve each proportion. 2 5 34 y =

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Solve each proportion. 7 n 32.1 =

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Example Problem Recycling 2,000 pounds of paper saves about 17 trees. Write and solve a proportion to determine how many trees you would expect to save by recycling 5,000 pounds of paper.

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Up Next… Activity 1: Gasoline Prices

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