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Finding the Fourth Proportional to 139.20, 208.95 and 81.48

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Solution

The fourth proportional to 139.20, 208.95 and 81.48 is: 122.31

Step by Step Solution

  1. Step 1: Write the proportion equation
    139.20 : 208.95 = 81.48 : x
  2. Step 2: Convert to fraction form
    139.20/208.95 = 81.48/x
  3. Step 3: Cross multiply
    139.20x = 208.95 × 81.48
  4. Step 4: Simplify right side
    139.20x = 17,025.72
  5. Step 5: Solve for x
    x = 17,025.72/139.20
  6. Step 6: Final answer
    x = 122.31

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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.