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Finding the Fourth Proportional to 129.20, 178.28 and 76.74

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Solution

The fourth proportional to 129.20, 178.28 and 76.74 is: 105.89

Step by Step Solution

  1. Step 1: Write the proportion equation
    129.20 : 178.28 = 76.74 : x
  2. Step 2: Convert to fraction form
    129.20/178.28 = 76.74/x
  3. Step 3: Cross multiply
    129.20x = 178.28 × 76.74
  4. Step 4: Simplify right side
    129.20x = 13,680.82
  5. Step 5: Solve for x
    x = 13,680.82/129.20
  6. Step 6: Final answer
    x = 105.89

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Why These Related Problems?

These problems maintain the same ratio (1.38) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.