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Finding the Fourth Proportional to 138.39, 207.57 and 90.20

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Solution

The fourth proportional to 138.39, 207.57 and 90.20 is: 135.28

Step by Step Solution

  1. Step 1: Write the proportion equation
    138.39 : 207.57 = 90.20 : x
  2. Step 2: Convert to fraction form
    138.39/207.57 = 90.20/x
  3. Step 3: Cross multiply
    138.39x = 207.57 × 90.20
  4. Step 4: Simplify right side
    138.39x = 18,721.78
  5. Step 5: Solve for x
    x = 18,721.78/138.39
  6. Step 6: Final answer
    x = 135.28

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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.