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Finding the Fourth Proportional to 138.08, 207.28 and 81.12

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Solution

The fourth proportional to 138.08, 207.28 and 81.12 is: 121.77

Step by Step Solution

  1. Step 1: Write the proportion equation
    138.08 : 207.28 = 81.12 : x
  2. Step 2: Convert to fraction form
    138.08/207.28 = 81.12/x
  3. Step 3: Cross multiply
    138.08x = 207.28 × 81.12
  4. Step 4: Simplify right side
    138.08x = 16,814.55
  5. Step 5: Solve for x
    x = 16,814.55/138.08
  6. Step 6: Final answer
    x = 121.77

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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.