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Finding the Fourth Proportional to 138, 206.96 and 77.20

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Solution

The fourth proportional to 138, 206.96 and 77.20 is: 115.78

Step by Step Solution

  1. Step 1: Write the proportion equation
    138 : 206.96 = 77.20 : x
  2. Step 2: Convert to fraction form
    138/206.96 = 77.20/x
  3. Step 3: Cross multiply
    138x = 206.96 × 77.20
  4. Step 4: Simplify right side
    138x = 15,977.31
  5. Step 5: Solve for x
    x = 15,977.31/138
  6. Step 6: Final answer
    x = 115.78

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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.