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Finding the Fourth Proportional to 81.45, 122.17 and 20.58

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Solution

The fourth proportional to 81.45, 122.17 and 20.58 is: 30.87

Step by Step Solution

  1. Step 1: Write the proportion equation
    81.45 : 122.17 = 20.58 : x
  2. Step 2: Convert to fraction form
    81.45/122.17 = 20.58/x
  3. Step 3: Cross multiply
    81.45x = 122.17 × 20.58
  4. Step 4: Simplify right side
    81.45x = 2,514.26
  5. Step 5: Solve for x
    x = 2,514.26/81.45
  6. Step 6: Final answer
    x = 30.87

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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.