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Finding the Fourth Proportional to 939.20, 1,408.80 and 391.38

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Solution

The fourth proportional to 939.20, 1,408.80 and 391.38 is: 587.07

Step by Step Solution

  1. Step 1: Write the proportion equation
    939.20 : 1,408.80 = 391.38 : x
  2. Step 2: Convert to fraction form
    939.20/1,408.80 = 391.38/x
  3. Step 3: Cross multiply
    939.20x = 1,408.80 × 391.38
  4. Step 4: Simplify right side
    939.20x = 551,376.14
  5. Step 5: Solve for x
    x = 551,376.14/939.20
  6. Step 6: Final answer
    x = 587.07

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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.