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Finding the Fourth Proportional to 686.47, 947.38 and 391.76

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Solution

The fourth proportional to 686.47, 947.38 and 391.76 is: 540.65

Step by Step Solution

  1. Step 1: Write the proportion equation
    686.47 : 947.38 = 391.76 : x
  2. Step 2: Convert to fraction form
    686.47/947.38 = 391.76/x
  3. Step 3: Cross multiply
    686.47x = 947.38 × 391.76
  4. Step 4: Simplify right side
    686.47x = 371,139.87
  5. Step 5: Solve for x
    x = 371,139.87/686.47
  6. Step 6: Final answer
    x = 540.65

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1.5x scale

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.