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Finding the Fourth Proportional to 139.04, 208.40 and 81.28

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Solution

The fourth proportional to 139.04, 208.40 and 81.28 is: 121.83

Step by Step Solution

  1. Step 1: Write the proportion equation
    139.04 : 208.40 = 81.28 : x
  2. Step 2: Convert to fraction form
    139.04/208.40 = 81.28/x
  3. Step 3: Cross multiply
    139.04x = 208.40 × 81.28
  4. Step 4: Simplify right side
    139.04x = 16,938.75
  5. Step 5: Solve for x
    x = 16,938.75/139.04
  6. Step 6: Final answer
    x = 121.83

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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.