Use the cross products property EXAMPLE 1 Write original proportion. 8 15 = x 6 Solve the proportion =. 8 x 6 15 Cross products property Simplify. 120.

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

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

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

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

Write and solve a proportion EXAMPLE 3 x 280 = 8 amount of food 100 weight of seal SOLUTION STEP 1 Write a proportion involving two ratios that compare the amount of food with the weight of the seal. 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 ? Seals

Write and solve a proportion EXAMPLE 3 STEP 2 Solve the proportion x 280 = Write proportion = 100 x Cross products property 2240 = 100x Simplify = x Divide each side by 100. ANSWER A 280 pound seal should be fed 22.4 pounds of food per day.

EXAMPLE 1 Solve the proportion. Check your solution. GUIDED PRACTICE for Examples 1, 2, and 3 = 4 a ANSWER

EXAMPLE 2 GUIDED PRACTICE for Examples 1, 2, and 3 3 x = 2 x– ANSWER Solve the proportion. Check your solution.

EXAMPLE 2 GUIDED PRACTICE for Examples 1, 2, and 3 4 m 5 = m – ANSWER Solve the proportion. Check your solution.

EXAMPLE 3 GUIDED PRACTICE for Examples 1, 2, and ANSWER Solve the proportion. Check your solution. WHAT IF? In Example 3, suppose the seal weighs 260 pounds. How much food should the seal be fed per day ? 4.

EXAMP LE 4 Use the scale on a map Ma ps Use a metric ruler and the map of Ohio to estimate the distance between Cleveland and Cincinnati. SOLUTION From the map’s scale, 1 centimeter represents 85 kilometers. On the map, the distance between Cleveland and Cincinnati is about 4.2 centimeters.

EXAMP LE 4 Use the scale on a map Write and solve a proportion to find the distance d between the cities. = 4.2 d 1 centimeters 85 kilometers Cross products property d = 357 Simplify. ANSWER The actual distance between Cleveland and Cincinnati is about 357 kilometers. 1 d =

EXAMP LE 4 Use the scale on a map GUIDED PRACTICE for Example Use a metric ruler and the map in Example 4 to estimate the distance (in kilometers) between Columbus and Cleveland. about kmANSWER

EXAMP LE 4 Use the scale on a map GUIDED PRACTICE for Example 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. Model ships ANSWERabout 960 ft