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Finding the Fourth Proportional to 81.90, 122.91 and 66.87

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Solution

The fourth proportional to 81.90, 122.91 and 66.87 is: 100.35

Step by Step Solution

  1. Step 1: Write the proportion equation
    81.90 : 122.91 = 66.87 : x
  2. Step 2: Convert to fraction form
    81.90/122.91 = 66.87/x
  3. Step 3: Cross multiply
    81.90x = 122.91 × 66.87
  4. Step 4: Simplify right side
    81.90x = 8,218.99
  5. Step 5: Solve for x
    x = 8,218.99/81.90
  6. Step 6: Final answer
    x = 100.35

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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.