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Finding the Fourth Proportional to 138.72, 208.08 and 77.85

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Solution

The fourth proportional to 138.72, 208.08 and 77.85 is: 116.78

Step by Step Solution

  1. Step 1: Write the proportion equation
    138.72 : 208.08 = 77.85 : x
  2. Step 2: Convert to fraction form
    138.72/208.08 = 77.85/x
  3. Step 3: Cross multiply
    138.72x = 208.08 × 77.85
  4. Step 4: Simplify right side
    138.72x = 16,199.03
  5. Step 5: Solve for x
    x = 16,199.03/138.72
  6. Step 6: Final answer
    x = 116.78

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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.