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Finding the Fourth Proportional to 138.89, 208.15 and 81.05

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Solution

The fourth proportional to 138.89, 208.15 and 81.05 is: 121.46

Step by Step Solution

  1. Step 1: Write the proportion equation
    138.89 : 208.15 = 81.05 : x
  2. Step 2: Convert to fraction form
    138.89/208.15 = 81.05/x
  3. Step 3: Cross multiply
    138.89x = 208.15 × 81.05
  4. Step 4: Simplify right side
    138.89x = 16,869.31
  5. Step 5: Solve for x
    x = 16,869.31/138.89
  6. Step 6: Final answer
    x = 121.46

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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.