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Finding the Fourth Proportional to 81.85, 122.77 and 20.98

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Solution

The fourth proportional to 81.85, 122.77 and 20.98 is: 31.47

Step by Step Solution

  1. Step 1: Write the proportion equation
    81.85 : 122.77 = 20.98 : x
  2. Step 2: Convert to fraction form
    81.85/122.77 = 20.98/x
  3. Step 3: Cross multiply
    81.85x = 122.77 × 20.98
  4. Step 4: Simplify right side
    81.85x = 2,575.93
  5. Step 5: Solve for x
    x = 2,575.93/81.85
  6. Step 6: Final answer
    x = 31.47

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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.