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Finding the Fourth Proportional to 138.71, 208.20 and 77.89

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Solution

The fourth proportional to 138.71, 208.20 and 77.89 is: 116.91

Step by Step Solution

  1. Step 1: Write the proportion equation
    138.71 : 208.20 = 77.89 : x
  2. Step 2: Convert to fraction form
    138.71/208.20 = 77.89/x
  3. Step 3: Cross multiply
    138.71x = 208.20 × 77.89
  4. Step 4: Simplify right side
    138.71x = 16,216.70
  5. Step 5: Solve for x
    x = 16,216.70/138.71
  6. Step 6: Final answer
    x = 116.91

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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.