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Finding the Fourth Proportional to 686.43, 947.42 and 420.79

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Solution

The fourth proportional to 686.43, 947.42 and 420.79 is: 580.78

Step by Step Solution

  1. Step 1: Write the proportion equation
    686.43 : 947.42 = 420.79 : x
  2. Step 2: Convert to fraction form
    686.43/947.42 = 420.79/x
  3. Step 3: Cross multiply
    686.43x = 947.42 × 420.79
  4. Step 4: Simplify right side
    686.43x = 398,664.86
  5. Step 5: Solve for x
    x = 398,664.86/686.43
  6. Step 6: Final answer
    x = 580.78

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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.