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Finding the Fourth Proportional to 939.78, 1,408.68 and 391.20

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Solution

The fourth proportional to 939.78, 1,408.68 and 391.20 is: 586.39

Step by Step Solution

  1. Step 1: Write the proportion equation
    939.78 : 1,408.68 = 391.20 : x
  2. Step 2: Convert to fraction form
    939.78/1,408.68 = 391.20/x
  3. Step 3: Cross multiply
    939.78x = 1,408.68 × 391.20
  4. Step 4: Simplify right side
    939.78x = 551,075.62
  5. Step 5: Solve for x
    x = 551,075.62/939.78
  6. Step 6: Final answer
    x = 586.39

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Why These Related Problems?

These problems maintain the same ratio (1.50) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.