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Finding the Fourth Proportional to 85.92, 128.85 and 51.90

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Solution

The fourth proportional to 85.92, 128.85 and 51.90 is: 77.83

Step by Step Solution

  1. Step 1: Write the proportion equation
    85.92 : 128.85 = 51.90 : x
  2. Step 2: Convert to fraction form
    85.92/128.85 = 51.90/x
  3. Step 3: Cross multiply
    85.92x = 128.85 × 51.90
  4. Step 4: Simplify right side
    85.92x = 6,687.32
  5. Step 5: Solve for x
    x = 6,687.32/85.92
  6. Step 6: Final answer
    x = 77.83

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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.