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Finding the Fourth Proportional to 139.78, 209.70 and 54.28

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Solution

The fourth proportional to 139.78, 209.70 and 54.28 is: 81.43

Step by Step Solution

  1. Step 1: Write the proportion equation
    139.78 : 209.70 = 54.28 : x
  2. Step 2: Convert to fraction form
    139.78/209.70 = 54.28/x
  3. Step 3: Cross multiply
    139.78x = 209.70 × 54.28
  4. Step 4: Simplify right side
    139.78x = 11,382.52
  5. Step 5: Solve for x
    x = 11,382.52/139.78
  6. Step 6: Final answer
    x = 81.43

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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.