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Finding the Fourth Proportional to 686.55, 947.43 and 391.89

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Solution

The fourth proportional to 686.55, 947.43 and 391.89 is: 540.80

Step by Step Solution

  1. Step 1: Write the proportion equation
    686.55 : 947.43 = 391.89 : x
  2. Step 2: Convert to fraction form
    686.55/947.43 = 391.89/x
  3. Step 3: Cross multiply
    686.55x = 947.43 × 391.89
  4. Step 4: Simplify right side
    686.55x = 371,288.34
  5. Step 5: Solve for x
    x = 371,288.34/686.55
  6. Step 6: Final answer
    x = 540.80

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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.