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Finding the Fourth Proportional to 138, 206.72 and 77.12

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Solution

The fourth proportional to 138, 206.72 and 77.12 is: 115.52

Step by Step Solution

  1. Step 1: Write the proportion equation
    138 : 206.72 = 77.12 : x
  2. Step 2: Convert to fraction form
    138/206.72 = 77.12/x
  3. Step 3: Cross multiply
    138x = 206.72 × 77.12
  4. Step 4: Simplify right side
    138x = 15,942.25
  5. Step 5: Solve for x
    x = 15,942.25/138
  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.