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Finding the Fourth Proportional to 861.92, 1,291.62 and 428.21

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Solution

The fourth proportional to 861.92, 1,291.62 and 428.21 is: 641.69

Step by Step Solution

  1. Step 1: Write the proportion equation
    861.92 : 1,291.62 = 428.21 : x
  2. Step 2: Convert to fraction form
    861.92/1,291.62 = 428.21/x
  3. Step 3: Cross multiply
    861.92x = 1,291.62 × 428.21
  4. Step 4: Simplify right side
    861.92x = 553,084.60
  5. Step 5: Solve for x
    x = 553,084.60/861.92
  6. Step 6: Final answer
    x = 641.69

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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.