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Finding the Fourth Proportional to 138.54, 207.61 and 128.42

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Solution

The fourth proportional to 138.54, 207.61 and 128.42 is: 192.43

Step by Step Solution

  1. Step 1: Write the proportion equation
    138.54 : 207.61 = 128.42 : x
  2. Step 2: Convert to fraction form
    138.54/207.61 = 128.42/x
  3. Step 3: Cross multiply
    138.54x = 207.61 × 128.42
  4. Step 4: Simplify right side
    138.54x = 26,659.92
  5. Step 5: Solve for x
    x = 26,659.92/138.54
  6. Step 6: Final answer
    x = 192.43

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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.