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Finding the Fourth Proportional to 861.78, 1,291.90 and 398.92

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Solution

The fourth proportional to 861.78, 1,291.90 and 398.92 is: 598.02

Step by Step Solution

  1. Step 1: Write the proportion equation
    861.78 : 1,291.90 = 398.92 : x
  2. Step 2: Convert to fraction form
    861.78/1,291.90 = 398.92/x
  3. Step 3: Cross multiply
    861.78x = 1,291.90 × 398.92
  4. Step 4: Simplify right side
    861.78x = 515,363.75
  5. Step 5: Solve for x
    x = 515,363.75/861.78
  6. Step 6: Final answer
    x = 598.02

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Why These Related Problems?

These problems maintain the same ratio (1.50) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.