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Finding the Fourth Proportional to 138.78, 208.31 and 66.69

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Solution

The fourth proportional to 138.78, 208.31 and 66.69 is: 100.10

Step by Step Solution

  1. Step 1: Write the proportion equation
    138.78 : 208.31 = 66.69 : x
  2. Step 2: Convert to fraction form
    138.78/208.31 = 66.69/x
  3. Step 3: Cross multiply
    138.78x = 208.31 × 66.69
  4. Step 4: Simplify right side
    138.78x = 13,891.86
  5. Step 5: Solve for x
    x = 13,891.86/138.78
  6. Step 6: Final answer
    x = 100.10

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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.