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Finding the Fourth Proportional to 861, 1,291.20 and 427.92

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Solution

The fourth proportional to 861, 1,291.20 and 427.92 is: 641.73

Step by Step Solution

  1. Step 1: Write the proportion equation
    861 : 1,291.20 = 427.92 : x
  2. Step 2: Convert to fraction form
    861/1,291.20 = 427.92/x
  3. Step 3: Cross multiply
    861x = 1,291.20 × 427.92
  4. Step 4: Simplify right side
    861x = 552,530.30
  5. Step 5: Solve for x
    x = 552,530.30/861
  6. Step 6: Final answer
    x = 641.73

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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.