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Finding the Fourth Proportional to 138.98, 208.66 and 66.90

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Solution

The fourth proportional to 138.98, 208.66 and 66.90 is: 100.44

Step by Step Solution

  1. Step 1: Write the proportion equation
    138.98 : 208.66 = 66.90 : x
  2. Step 2: Convert to fraction form
    138.98/208.66 = 66.90/x
  3. Step 3: Cross multiply
    138.98x = 208.66 × 66.90
  4. Step 4: Simplify right side
    138.98x = 13,959.35
  5. Step 5: Solve for x
    x = 13,959.35/138.98
  6. Step 6: Final answer
    x = 100.44

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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.