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Finding the Fourth Proportional to 139.62, 209.38 and 81.87

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Solution

The fourth proportional to 139.62, 209.38 and 81.87 is: 122.78

Step by Step Solution

  1. Step 1: Write the proportion equation
    139.62 : 209.38 = 81.87 : x
  2. Step 2: Convert to fraction form
    139.62/209.38 = 81.87/x
  3. Step 3: Cross multiply
    139.62x = 209.38 × 81.87
  4. Step 4: Simplify right side
    139.62x = 17,141.94
  5. Step 5: Solve for x
    x = 17,141.94/139.62
  6. Step 6: Final answer
    x = 122.78

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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.