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Finding the Fourth Proportional to 139.14, 208.85 and 81.42

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Solution

The fourth proportional to 139.14, 208.85 and 81.42 is: 122.22

Step by Step Solution

  1. Step 1: Write the proportion equation
    139.14 : 208.85 = 81.42 : x
  2. Step 2: Convert to fraction form
    139.14/208.85 = 81.42/x
  3. Step 3: Cross multiply
    139.14x = 208.85 × 81.42
  4. Step 4: Simplify right side
    139.14x = 17,004.77
  5. Step 5: Solve for x
    x = 17,004.77/139.14
  6. Step 6: Final answer
    x = 122.22

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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.