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Finding the Fourth Proportional to 129.20, 193.76 and 81.40

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Solution

The fourth proportional to 129.20, 193.76 and 81.40 is: 122.07

Step by Step Solution

  1. Step 1: Write the proportion equation
    129.20 : 193.76 = 81.40 : x
  2. Step 2: Convert to fraction form
    129.20/193.76 = 81.40/x
  3. Step 3: Cross multiply
    129.20x = 193.76 × 81.40
  4. Step 4: Simplify right side
    129.20x = 15,772.06
  5. Step 5: Solve for x
    x = 15,772.06/129.20
  6. Step 6: Final answer
    x = 122.07

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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.