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Finding the Fourth Proportional to 138.20, 206.87 and 77.18

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Solution

The fourth proportional to 138.20, 206.87 and 77.18 is: 115.52

Step by Step Solution

  1. Step 1: Write the proportion equation
    138.20 : 206.87 = 77.18 : x
  2. Step 2: Convert to fraction form
    138.20/206.87 = 77.18/x
  3. Step 3: Cross multiply
    138.20x = 206.87 × 77.18
  4. Step 4: Simplify right side
    138.20x = 15,964.81
  5. Step 5: Solve for x
    x = 15,964.81/138.20
  6. Step 6: Final answer
    x = 115.52

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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.