EXAMPLE 1 Use the cross products property Solve

EXAMPLE 1 Use the cross products property CHECK 8 ? 6 = 20 15

EXAMPLE 2 Standardized Test Practice What is the value of x in the proportion

EXAMPLE 2 Standardized Test Practice ANSWER The value of x is – 3. The

EXAMPLE 3 Write and solve a proportion Seals Each day, the seals at an

EXAMPLE 3 Write and solve a proportion STEP 2 Solve the proportion. 8 x

EXAMPLE 1 GUIDED PRACTICE for Examples 1, 2, and 3 Solve the proportion. Check

EXAMPLE 1 for Examples 1, 2, and 3 Use the cross products property GUIDED

EXAMPLE 2 GUIDED PRACTICE 2. for Examples 1, 2, and 3 2 3 =

EXAMPLE 1 GUIDED PRACTICE for Examples 1, 2, and 3 CHECK 3 ? 2

EXAMPLE 2 GUIDED PRACTICE 3. for Examples 1, 2, and 3 m m– 6

EXAMPLE 3 GUIDED PRACTICE for Examples 1, 2, and 3 4. WHAT IF? In

EXAMPLE 3 Examples 1, 2, and 3 GUIDED PRACTICE Write andfor solve a proportion

EXAMPLE 4 Use the scale on a map Maps Use a metric ruler and

Use the scale on a map EXAMPLE 4 Write and solve a proportion to

Use the on a 4 map EXAMPLE 4 for scale Example GUIDED PRACTICE 5.

Use the on a 4 map EXAMPLE 4 for scale Example GUIDED PRACTICE Model

Use the on a 4 map EXAMPLE 4 for scale Example GUIDED PRACTICE SOLUTION

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EXAMPLE 1 Use the cross products property Solve the proportion 8 = 6 x 15 8 15 = x 6 120 = 6 x 20 = x Write original proportion. Cross products property Simplify. Divide each side by 6. ANSWER The solution is 20. Check by substituting 20 for x in the original proportion.

EXAMPLE 1 Use the cross products property CHECK 8 ? 6 = 20 15 ? 20 6 8 15 = 120 Substitute 20 for x. Cross products property Simplify. Solution checks.

EXAMPLE 2 Standardized Test Practice What is the value of x in the proportion 4 = 8 ? x x– 3 A – 6 SOLUTION 4 = 8 x x – 3 B – 3 C 3 D 6 Write original proportion. 4(x – 3) = x 8 Cross products property 4 x – 12 = 8 x Simplify. – 12 = 4 x Subtract 4 x from each side. – 3=x Divide each side by 4.

EXAMPLE 2 Standardized Test Practice ANSWER The value of x is – 3. The correct answer is B. A B C D

EXAMPLE 3 Write and solve a proportion Seals Each day, the seals at an aquarium are each fed 8 pounds of food for every 100 pounds of their body weight. A seal at the aquarium weighs 280 pounds. How much food should the seal be fed per day ? SOLUTION STEP 1 Write a proportion involving two ratios that compare the amount of food with the weight of the seal. 8 x = 100 280 amount of food weight of seal

EXAMPLE 3 Write and solve a proportion STEP 2 Solve the proportion. 8 x = 100 280 8 280 = 100 x Write proportion. Cross products property 2240 = 100 x Simplify. 22. 4 = x Divide each side by 100. ANSWER A 280 pound seal should be fed 22. 4 pounds of food per day.

EXAMPLE 1 GUIDED PRACTICE for Examples 1, 2, and 3 Solve the proportion. Check your solution. 1. 4 = 24 a 30 30 4 = a 24 Cross products property 120 = 24 a Simplify. 5= a Write original proportion. Divide each side by 24. ANSWER The solution is 5. Check by substituting 5 for a in the original proportion.

EXAMPLE 1 for Examples 1, 2, and 3 Use the cross products property GUIDED PRACTICE CHECK 4 ? 24 = 5 30 ? 30 4 = 24 5 120 = 120 Substitute 5 for a. Cross products property Simplify. Solution checks.

EXAMPLE 2 GUIDED PRACTICE 2. for Examples 1, 2, and 3 2 3 = x x – 6 3 = 2 x x – 6 Write original proportion. 3(x – 6) = 2 x Cross products property 3 x – 18 = 2 x Distrubutive property 18 = x Subtract 3 x from each side. ANSWER The value of x is 18. Check by substituting 18 for x in the original proportion.

EXAMPLE 1 GUIDED PRACTICE for Examples 1, 2, and 3 CHECK 3 ? 2 = 18 18 – 6 ? 3(18 – 6) = 18 2 ? 54 – 18 = 36 36 = 36 Substitute 18 for x. Cross products property Simplify. Solution checks.

EXAMPLE 2 GUIDED PRACTICE 3. for Examples 1, 2, and 3 m m– 6 = 5 4 Write original proportion. m 4 = 5(m – 6) Cross products property 4 m = 5 m – 30 m = 30 Simplify Subtract 5 m from each side.

EXAMPLE 3 GUIDED PRACTICE for Examples 1, 2, and 3 4. WHAT IF? In Example 3, suppose the seal weights 260 pounds. How much food should the seal be fed per day? SOLUTION STEP 1 Write a proportion involving two ratios that compare the amount of food with the weight of the seal. 8 x = 100 260 amount of food weight of seal

EXAMPLE 3 Examples 1, 2, and 3 GUIDED PRACTICE Write andfor solve a proportion STEP 2 Solve the proportion. 8 x = 100 260 8 260 = 100 x Write proportion. Cross products property 2080 = 100 x Simplify. 20. 8 = x Divide each side by 100. ANSWER A 260 pound seal should be fed 20. 8 pounds of food per day.

EXAMPLE 4 Use the scale on a map Maps Use a metric ruler and the map of Ohio to estimate the distance between Cleveland Cincinnati. SOLUTION From the map’s scale, 1 centimeter represents 85 kilometers. On the map, the distance between Cleveland Cincinnati is about 4. 2 centimeters.

Use the scale on a map EXAMPLE 4 Write and solve a proportion to find the distance d between the cities. 1 85 4. 2 = d 1 d = 85 4. 2 d = 357 centimeters kilometers Cross products property Simplify. ANSWER The actual distance between Cleveland Cincinnati is about 357 kilometers.

Use the on a 4 map EXAMPLE 4 for scale Example GUIDED PRACTICE 5. Use a metric ruler and the map in Example 4 to estimate the distance (in kilometers) between Columbus and Cleveland. SOLUTION It is about 212. 5 km

Use the on a 4 map EXAMPLE 4 for scale Example GUIDED PRACTICE Model ships 6. The ship model kits sold at a hobby store have a scale of 1 ft : 600 ft. A completed model of the Queen Elizabeth II is 1. 6 feet long. Estimate the actual length of the Queen Elizabeth II.

Use the on a 4 map EXAMPLE 4 for scale Example GUIDED PRACTICE SOLUTION Write and solve a proportion to find the length l of the Queen Elizabeth II. 1 600 1. 6 = l 1. l = 600. 1. 6 l = 960 Cross products property Simplify. ANSWER The actual length of the Queen Elizabeth II is about 960 feet.