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Finding the Fourth Proportional to 81.96, 122.89 and 39.21

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Solution

The fourth proportional to 81.96, 122.89 and 39.21 is: 58.79

Step by Step Solution

  1. Step 1: Write the proportion equation
    81.96 : 122.89 = 39.21 : x
  2. Step 2: Convert to fraction form
    81.96/122.89 = 39.21/x
  3. Step 3: Cross multiply
    81.96x = 122.89 × 39.21
  4. Step 4: Simplify right side
    81.96x = 4,818.52
  5. Step 5: Solve for x
    x = 4,818.52/81.96
  6. Step 6: Final answer
    x = 58.79

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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.