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Finding the Fourth Proportional to 861.89, 1,292.55 and 428.75

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Solution

The fourth proportional to 861.89, 1,292.55 and 428.75 is: 642.98

Step by Step Solution

  1. Step 1: Write the proportion equation
    861.89 : 1,292.55 = 428.75 : x
  2. Step 2: Convert to fraction form
    861.89/1,292.55 = 428.75/x
  3. Step 3: Cross multiply
    861.89x = 1,292.55 × 428.75
  4. Step 4: Simplify right side
    861.89x = 554,180.81
  5. Step 5: Solve for x
    x = 554,180.81/861.89
  6. Step 6: Final answer
    x = 642.98

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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.