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Finding the Fourth Proportional to 129.72, 178.94 and 100.20

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Solution

The fourth proportional to 129.72, 178.94 and 100.20 is: 138.22

Step by Step Solution

  1. Step 1: Write the proportion equation
    129.72 : 178.94 = 100.20 : x
  2. Step 2: Convert to fraction form
    129.72/178.94 = 100.20/x
  3. Step 3: Cross multiply
    129.72x = 178.94 × 100.20
  4. Step 4: Simplify right side
    129.72x = 17,929.79
  5. Step 5: Solve for x
    x = 17,929.79/129.72
  6. Step 6: Final answer
    x = 138.22

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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.