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Finding the Fourth Proportional to 139.12, 208.49 and 78.13

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Solution

The fourth proportional to 139.12, 208.49 and 78.13 is: 117.09

Step by Step Solution

  1. Step 1: Write the proportion equation
    139.12 : 208.49 = 78.13 : x
  2. Step 2: Convert to fraction form
    139.12/208.49 = 78.13/x
  3. Step 3: Cross multiply
    139.12x = 208.49 × 78.13
  4. Step 4: Simplify right side
    139.12x = 16,289.32
  5. Step 5: Solve for x
    x = 16,289.32/139.12
  6. Step 6: Final answer
    x = 117.09

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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.