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Finding the Fourth Proportional to 139.18, 208.78 and 47.85

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Solution

The fourth proportional to 139.18, 208.78 and 47.85 is: 71.78

Step by Step Solution

  1. Step 1: Write the proportion equation
    139.18 : 208.78 = 47.85 : x
  2. Step 2: Convert to fraction form
    139.18/208.78 = 47.85/x
  3. Step 3: Cross multiply
    139.18x = 208.78 × 47.85
  4. Step 4: Simplify right side
    139.18x = 9,990.12
  5. Step 5: Solve for x
    x = 9,990.12/139.18
  6. Step 6: Final answer
    x = 71.78

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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.