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Finding the Fourth Proportional to 86.18, 129.41 and 81.85

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Solution

The fourth proportional to 86.18, 129.41 and 81.85 is: 122.91

Step by Step Solution

  1. Step 1: Write the proportion equation
    86.18 : 129.41 = 81.85 : x
  2. Step 2: Convert to fraction form
    86.18/129.41 = 81.85/x
  3. Step 3: Cross multiply
    86.18x = 129.41 × 81.85
  4. Step 4: Simplify right side
    86.18x = 10,592.21
  5. Step 5: Solve for x
    x = 10,592.21/86.18
  6. Step 6: Final answer
    x = 122.91

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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.