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Finding the Fourth Proportional to 129.72, 194.40 and 81.66

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Solution

The fourth proportional to 129.72, 194.40 and 81.66 is: 122.38

Step by Step Solution

  1. Step 1: Write the proportion equation
    129.72 : 194.40 = 81.66 : x
  2. Step 2: Convert to fraction form
    129.72/194.40 = 81.66/x
  3. Step 3: Cross multiply
    129.72x = 194.40 × 81.66
  4. Step 4: Simplify right side
    129.72x = 15,874.70
  5. Step 5: Solve for x
    x = 15,874.70/129.72
  6. Step 6: Final answer
    x = 122.38

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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.