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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Presentation transcript:

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.