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Finding the Fourth Proportional to 686.56, 947.38 and 391.80

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Solution

The fourth proportional to 686.56, 947.38 and 391.80 is: 540.64

Step by Step Solution

  1. Step 1: Write the proportion equation
    686.56 : 947.38 = 391.80 : x
  2. Step 2: Convert to fraction form
    686.56/947.38 = 391.80/x
  3. Step 3: Cross multiply
    686.56x = 947.38 × 391.80
  4. Step 4: Simplify right side
    686.56x = 371,183.48
  5. Step 5: Solve for x
    x = 371,183.48/686.56
  6. Step 6: Final answer
    x = 540.64

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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.