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Finding the Fourth Proportional to 138.96, 208.56 and 66.90

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Solution

The fourth proportional to 138.96, 208.56 and 66.90 is: 100.41

Step by Step Solution

  1. Step 1: Write the proportion equation
    138.96 : 208.56 = 66.90 : x
  2. Step 2: Convert to fraction form
    138.96/208.56 = 66.90/x
  3. Step 3: Cross multiply
    138.96x = 208.56 × 66.90
  4. Step 4: Simplify right side
    138.96x = 13,952.66
  5. Step 5: Solve for x
    x = 13,952.66/138.96
  6. Step 6: Final answer
    x = 100.41

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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.