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Finding the Fourth Proportional to 138.94, 208.34 and 81.18

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Solution

The fourth proportional to 138.94, 208.34 and 81.18 is: 121.72

Step by Step Solution

  1. Step 1: Write the proportion equation
    138.94 : 208.34 = 81.18 : x
  2. Step 2: Convert to fraction form
    138.94/208.34 = 81.18/x
  3. Step 3: Cross multiply
    138.94x = 208.34 × 81.18
  4. Step 4: Simplify right side
    138.94x = 16,911.59
  5. Step 5: Solve for x
    x = 16,911.59/138.94
  6. Step 6: Final answer
    x = 121.72

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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.