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Finding the Fourth Proportional to 139.75, 209.31 and 85.48

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Solution

The fourth proportional to 139.75, 209.31 and 85.48 is: 128.02

Step by Step Solution

  1. Step 1: Write the proportion equation
    139.75 : 209.31 = 85.48 : x
  2. Step 2: Convert to fraction form
    139.75/209.31 = 85.48/x
  3. Step 3: Cross multiply
    139.75x = 209.31 × 85.48
  4. Step 4: Simplify right side
    139.75x = 17,890.77
  5. Step 5: Solve for x
    x = 17,890.77/139.75
  6. Step 6: Final answer
    x = 128.02

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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.