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Finding the Fourth Proportional to 139.28, 208.62 and 81.32

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Solution

The fourth proportional to 139.28, 208.62 and 81.32 is: 121.80

Step by Step Solution

  1. Step 1: Write the proportion equation
    139.28 : 208.62 = 81.32 : x
  2. Step 2: Convert to fraction form
    139.28/208.62 = 81.32/x
  3. Step 3: Cross multiply
    139.28x = 208.62 × 81.32
  4. Step 4: Simplify right side
    139.28x = 16,963.94
  5. Step 5: Solve for x
    x = 16,963.94/139.28
  6. Step 6: Final answer
    x = 121.80

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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.