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Finding the Fourth Proportional to 139.68, 209.51 and 85.91

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Solution

The fourth proportional to 139.68, 209.51 and 85.91 is: 128.85

Step by Step Solution

  1. Step 1: Write the proportion equation
    139.68 : 209.51 = 85.91 : x
  2. Step 2: Convert to fraction form
    139.68/209.51 = 85.91/x
  3. Step 3: Cross multiply
    139.68x = 209.51 × 85.91
  4. Step 4: Simplify right side
    139.68x = 17,997.53
  5. Step 5: Solve for x
    x = 17,997.53/139.68
  6. Step 6: Final answer
    x = 128.85

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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.