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Finding the Fourth Proportional to 139.57, 209.51 and 81.86

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Solution

The fourth proportional to 139.57, 209.51 and 81.86 is: 122.88

Step by Step Solution

  1. Step 1: Write the proportion equation
    139.57 : 209.51 = 81.86 : x
  2. Step 2: Convert to fraction form
    139.57/209.51 = 81.86/x
  3. Step 3: Cross multiply
    139.57x = 209.51 × 81.86
  4. Step 4: Simplify right side
    139.57x = 17,150.49
  5. Step 5: Solve for x
    x = 17,150.49/139.57
  6. Step 6: Final answer
    x = 122.88

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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.