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Finding the Fourth Proportional to 686.38, 947.28 and 391.70

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Solution

The fourth proportional to 686.38, 947.28 and 391.70 is: 540.59

Step by Step Solution

  1. Step 1: Write the proportion equation
    686.38 : 947.28 = 391.70 : x
  2. Step 2: Convert to fraction form
    686.38/947.28 = 391.70/x
  3. Step 3: Cross multiply
    686.38x = 947.28 × 391.70
  4. Step 4: Simplify right side
    686.38x = 371,046.31
  5. Step 5: Solve for x
    x = 371,046.31/686.38
  6. Step 6: Final answer
    x = 540.59

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Why These Related Problems?

These problems maintain the same ratio (1.38) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.