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Finding the Fourth Proportional to 129.72, 178.92 and 105.42

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Solution

The fourth proportional to 129.72, 178.92 and 105.42 is: 145.40

Step by Step Solution

  1. Step 1: Write the proportion equation
    129.72 : 178.92 = 105.42 : x
  2. Step 2: Convert to fraction form
    129.72/178.92 = 105.42/x
  3. Step 3: Cross multiply
    129.72x = 178.92 × 105.42
  4. Step 4: Simplify right side
    129.72x = 18,861.75
  5. Step 5: Solve for x
    x = 18,861.75/129.72
  6. Step 6: Final answer
    x = 145.40

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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.