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Finding the Fourth Proportional to 138.86, 208.09 and 77.21

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Solution

The fourth proportional to 138.86, 208.09 and 77.21 is: 115.70

Step by Step Solution

  1. Step 1: Write the proportion equation
    138.86 : 208.09 = 77.21 : x
  2. Step 2: Convert to fraction form
    138.86/208.09 = 77.21/x
  3. Step 3: Cross multiply
    138.86x = 208.09 × 77.21
  4. Step 4: Simplify right side
    138.86x = 16,065.20
  5. Step 5: Solve for x
    x = 16,065.20/138.86
  6. Step 6: Final answer
    x = 115.70

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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.