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Finding the Fourth Proportional to 138.72, 207.78 and 90.64

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Solution

The fourth proportional to 138.72, 207.78 and 90.64 is: 135.76

Step by Step Solution

  1. Step 1: Write the proportion equation
    138.72 : 207.78 = 90.64 : x
  2. Step 2: Convert to fraction form
    138.72/207.78 = 90.64/x
  3. Step 3: Cross multiply
    138.72x = 207.78 × 90.64
  4. Step 4: Simplify right side
    138.72x = 18,833.18
  5. Step 5: Solve for x
    x = 18,833.18/138.72
  6. Step 6: Final answer
    x = 135.76

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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.