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Finding the Fourth Proportional to 81.72, 122.78 and 57.82

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Solution

The fourth proportional to 81.72, 122.78 and 57.82 is: 86.87

Step by Step Solution

  1. Step 1: Write the proportion equation
    81.72 : 122.78 = 57.82 : x
  2. Step 2: Convert to fraction form
    81.72/122.78 = 57.82/x
  3. Step 3: Cross multiply
    81.72x = 122.78 × 57.82
  4. Step 4: Simplify right side
    81.72x = 7,098.85
  5. Step 5: Solve for x
    x = 7,098.85/81.72
  6. Step 6: Final answer
    x = 86.87

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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.