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Finding the Fourth Proportional to 861.39, 1,291.44 and 428.85

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Solution

The fourth proportional to 861.39, 1,291.44 and 428.85 is: 642.95

Step by Step Solution

  1. Step 1: Write the proportion equation
    861.39 : 1,291.44 = 428.85 : x
  2. Step 2: Convert to fraction form
    861.39/1,291.44 = 428.85/x
  3. Step 3: Cross multiply
    861.39x = 1,291.44 × 428.85
  4. Step 4: Simplify right side
    861.39x = 553,834.04
  5. Step 5: Solve for x
    x = 553,834.04/861.39
  6. Step 6: Final answer
    x = 642.95

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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.