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Finding the Fourth Proportional to 139.08, 208.09 and 81.35

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Solution

The fourth proportional to 139.08, 208.09 and 81.35 is: 121.72

Step by Step Solution

  1. Step 1: Write the proportion equation
    139.08 : 208.09 = 81.35 : x
  2. Step 2: Convert to fraction form
    139.08/208.09 = 81.35/x
  3. Step 3: Cross multiply
    139.08x = 208.09 × 81.35
  4. Step 4: Simplify right side
    139.08x = 16,928.68
  5. Step 5: Solve for x
    x = 16,928.68/139.08
  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.