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Finding the Fourth Proportional to 129.66, 178.71 and 90.78

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Solution

The fourth proportional to 129.66, 178.71 and 90.78 is: 125.12

Step by Step Solution

  1. Step 1: Write the proportion equation
    129.66 : 178.71 = 90.78 : x
  2. Step 2: Convert to fraction form
    129.66/178.71 = 90.78/x
  3. Step 3: Cross multiply
    129.66x = 178.71 × 90.78
  4. Step 4: Simplify right side
    129.66x = 16,223.29
  5. Step 5: Solve for x
    x = 16,223.29/129.66
  6. Step 6: Final answer
    x = 125.12

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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.