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Finding the Fourth Proportional to 81.90, 122.72 and 54.86

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Solution

The fourth proportional to 81.90, 122.72 and 54.86 is: 82.20

Step by Step Solution

  1. Step 1: Write the proportion equation
    81.90 : 122.72 = 54.86 : x
  2. Step 2: Convert to fraction form
    81.90/122.72 = 54.86/x
  3. Step 3: Cross multiply
    81.90x = 122.72 × 54.86
  4. Step 4: Simplify right side
    81.90x = 6,732.42
  5. Step 5: Solve for x
    x = 6,732.42/81.90
  6. Step 6: Final answer
    x = 82.20

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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.