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Finding the Fourth Proportional to 139.69, 209.67 and 78.87

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Solution

The fourth proportional to 139.69, 209.67 and 78.87 is: 118.39

Step by Step Solution

  1. Step 1: Write the proportion equation
    139.69 : 209.67 = 78.87 : x
  2. Step 2: Convert to fraction form
    139.69/209.67 = 78.87/x
  3. Step 3: Cross multiply
    139.69x = 209.67 × 78.87
  4. Step 4: Simplify right side
    139.69x = 16,537.61
  5. Step 5: Solve for x
    x = 16,537.61/139.69
  6. Step 6: Final answer
    x = 118.39

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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.