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Finding the Fourth Proportional to 938.78, 1,408.31 and 390.99

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Solution

The fourth proportional to 938.78, 1,408.31 and 390.99 is: 586.54

Step by Step Solution

  1. Step 1: Write the proportion equation
    938.78 : 1,408.31 = 390.99 : x
  2. Step 2: Convert to fraction form
    938.78/1,408.31 = 390.99/x
  3. Step 3: Cross multiply
    938.78x = 1,408.31 × 390.99
  4. Step 4: Simplify right side
    938.78x = 550,635.13
  5. Step 5: Solve for x
    x = 550,635.13/938.78
  6. Step 6: Final answer
    x = 586.54

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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.