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Finding the Fourth Proportional to 139.52, 209.32 and 85.76

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Solution

The fourth proportional to 139.52, 209.32 and 85.76 is: 128.66

Step by Step Solution

  1. Step 1: Write the proportion equation
    139.52 : 209.32 = 85.76 : x
  2. Step 2: Convert to fraction form
    139.52/209.32 = 85.76/x
  3. Step 3: Cross multiply
    139.52x = 209.32 × 85.76
  4. Step 4: Simplify right side
    139.52x = 17,951.28
  5. Step 5: Solve for x
    x = 17,951.28/139.52
  6. Step 6: Final answer
    x = 128.66

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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.