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Finding the Fourth Proportional to 81.78, 122.61 and 54.78

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Solution

The fourth proportional to 81.78, 122.61 and 54.78 is: 82.13

Step by Step Solution

  1. Step 1: Write the proportion equation
    81.78 : 122.61 = 54.78 : x
  2. Step 2: Convert to fraction form
    81.78/122.61 = 54.78/x
  3. Step 3: Cross multiply
    81.78x = 122.61 × 54.78
  4. Step 4: Simplify right side
    81.78x = 6,716.58
  5. Step 5: Solve for x
    x = 6,716.58/81.78
  6. Step 6: Final answer
    x = 82.13

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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.