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Finding the Fourth Proportional to 129.36, 178.50 and 87.90

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Solution

The fourth proportional to 129.36, 178.50 and 87.90 is: 121.29

Step by Step Solution

  1. Step 1: Write the proportion equation
    129.36 : 178.50 = 87.90 : x
  2. Step 2: Convert to fraction form
    129.36/178.50 = 87.90/x
  3. Step 3: Cross multiply
    129.36x = 178.50 × 87.90
  4. Step 4: Simplify right side
    129.36x = 15,690.15
  5. Step 5: Solve for x
    x = 15,690.15/129.36
  6. Step 6: Final answer
    x = 121.29

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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.