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Finding the Fourth Proportional to 280.92, 421.29 and 85.85

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Solution

The fourth proportional to 280.92, 421.29 and 85.85 is: 128.75

Step by Step Solution

  1. Step 1: Write the proportion equation
    280.92 : 421.29 = 85.85 : x
  2. Step 2: Convert to fraction form
    280.92/421.29 = 85.85/x
  3. Step 3: Cross multiply
    280.92x = 421.29 × 85.85
  4. Step 4: Simplify right side
    280.92x = 36,167.75
  5. Step 5: Solve for x
    x = 36,167.75/280.92
  6. Step 6: Final answer
    x = 128.75

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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.