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Finding the Fourth Proportional to 81.69, 122.54 and 20.82

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Solution

The fourth proportional to 81.69, 122.54 and 20.82 is: 31.24

Step by Step Solution

  1. Step 1: Write the proportion equation
    81.69 : 122.54 = 20.82 : x
  2. Step 2: Convert to fraction form
    81.69/122.54 = 20.82/x
  3. Step 3: Cross multiply
    81.69x = 122.54 × 20.82
  4. Step 4: Simplify right side
    81.69x = 2,551.67
  5. Step 5: Solve for x
    x = 2,551.67/81.69
  6. Step 6: Final answer
    x = 31.24

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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.