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Finding the Fourth Proportional to 139.90, 209.70 and 85.83

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Solution

The fourth proportional to 139.90, 209.70 and 85.83 is: 128.65

Step by Step Solution

  1. Step 1: Write the proportion equation
    139.90 : 209.70 = 85.83 : x
  2. Step 2: Convert to fraction form
    139.90/209.70 = 85.83/x
  3. Step 3: Cross multiply
    139.90x = 209.70 × 85.83
  4. Step 4: Simplify right side
    139.90x = 17,998.55
  5. Step 5: Solve for x
    x = 17,998.55/139.90
  6. Step 6: Final answer
    x = 128.65

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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.