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Finding the Fourth Proportional to 139.39, 208.78 and 78.44

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Solution

The fourth proportional to 139.39, 208.78 and 78.44 is: 117.48

Step by Step Solution

  1. Step 1: Write the proportion equation
    139.39 : 208.78 = 78.44 : x
  2. Step 2: Convert to fraction form
    139.39/208.78 = 78.44/x
  3. Step 3: Cross multiply
    139.39x = 208.78 × 78.44
  4. Step 4: Simplify right side
    139.39x = 16,375.46
  5. Step 5: Solve for x
    x = 16,375.46/139.39
  6. Step 6: Final answer
    x = 117.48

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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.