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Finding the Fourth Proportional to 138.38, 207.72 and 80.64

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Solution

The fourth proportional to 138.38, 207.72 and 80.64 is: 121.05

Step by Step Solution

  1. Step 1: Write the proportion equation
    138.38 : 207.72 = 80.64 : x
  2. Step 2: Convert to fraction form
    138.38/207.72 = 80.64/x
  3. Step 3: Cross multiply
    138.38x = 207.72 × 80.64
  4. Step 4: Simplify right side
    138.38x = 16,750.54
  5. Step 5: Solve for x
    x = 16,750.54/138.38
  6. Step 6: Final answer
    x = 121.05

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Why These Related Problems?

These problems maintain the same ratio (1.50) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.