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Finding the Fourth Proportional to 129.45, 178.55 and 85.78

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Solution

The fourth proportional to 129.45, 178.55 and 85.78 is: 118.33

Step by Step Solution

  1. Step 1: Write the proportion equation
    129.45 : 178.55 = 85.78 : x
  2. Step 2: Convert to fraction form
    129.45/178.55 = 85.78/x
  3. Step 3: Cross multiply
    129.45x = 178.55 × 85.78
  4. Step 4: Simplify right side
    129.45x = 15,317.12
  5. Step 5: Solve for x
    x = 15,317.12/129.45
  6. Step 6: Final answer
    x = 118.33

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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.