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Finding the Fourth Proportional to 139, 208.19 and 78

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Solution

The fourth proportional to 139, 208.19 and 78 is: 116.83

Step by Step Solution

  1. Step 1: Write the proportion equation
    139 : 208.19 = 78 : x
  2. Step 2: Convert to fraction form
    139/208.19 = 78/x
  3. Step 3: Cross multiply
    139x = 208.19 × 78
  4. Step 4: Simplify right side
    139x = 16,238.82
  5. Step 5: Solve for x
    x = 16,238.82/139
  6. Step 6: Final answer
    x = 116.83

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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.