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Finding the Fourth Proportional to 686.50, 947.40 and 391.80

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Solution

The fourth proportional to 686.50, 947.40 and 391.80 is: 540.70

Step by Step Solution

  1. Step 1: Write the proportion equation
    686.50 : 947.40 = 391.80 : x
  2. Step 2: Convert to fraction form
    686.50/947.40 = 391.80/x
  3. Step 3: Cross multiply
    686.50x = 947.40 × 391.80
  4. Step 4: Simplify right side
    686.50x = 371,191.32
  5. Step 5: Solve for x
    x = 371,191.32/686.50
  6. Step 6: Final answer
    x = 540.70

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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.