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Finding the Fourth Proportional to 138.98, 208.41 and 74.78

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Solution

The fourth proportional to 138.98, 208.41 and 74.78 is: 112.14

Step by Step Solution

  1. Step 1: Write the proportion equation
    138.98 : 208.41 = 74.78 : x
  2. Step 2: Convert to fraction form
    138.98/208.41 = 74.78/x
  3. Step 3: Cross multiply
    138.98x = 208.41 × 74.78
  4. Step 4: Simplify right side
    138.98x = 15,584.90
  5. Step 5: Solve for x
    x = 15,584.90/138.98
  6. Step 6: Final answer
    x = 112.14

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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.