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Finding the Fourth Proportional to 81.26, 121.89 and 20.39

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Solution

The fourth proportional to 81.26, 121.89 and 20.39 is: 30.59

Step by Step Solution

  1. Step 1: Write the proportion equation
    81.26 : 121.89 = 20.39 : x
  2. Step 2: Convert to fraction form
    81.26/121.89 = 20.39/x
  3. Step 3: Cross multiply
    81.26x = 121.89 × 20.39
  4. Step 4: Simplify right side
    81.26x = 2,485.72
  5. Step 5: Solve for x
    x = 2,485.72/81.26
  6. Step 6: Final answer
    x = 30.59

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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.