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Finding the Fourth Proportional to 138.61, 207.69 and 77.86

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Solution

The fourth proportional to 138.61, 207.69 and 77.86 is: 116.66

Step by Step Solution

  1. Step 1: Write the proportion equation
    138.61 : 207.69 = 77.86 : x
  2. Step 2: Convert to fraction form
    138.61/207.69 = 77.86/x
  3. Step 3: Cross multiply
    138.61x = 207.69 × 77.86
  4. Step 4: Simplify right side
    138.61x = 16,170.74
  5. Step 5: Solve for x
    x = 16,170.74/138.61
  6. Step 6: Final answer
    x = 116.66

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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.