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Finding the Fourth Proportional to 81.29, 121.93 and 20.42

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Solution

The fourth proportional to 81.29, 121.93 and 20.42 is: 30.63

Step by Step Solution

  1. Step 1: Write the proportion equation
    81.29 : 121.93 = 20.42 : x
  2. Step 2: Convert to fraction form
    81.29/121.93 = 20.42/x
  3. Step 3: Cross multiply
    81.29x = 121.93 × 20.42
  4. Step 4: Simplify right side
    81.29x = 2,489.61
  5. Step 5: Solve for x
    x = 2,489.61/81.29
  6. Step 6: Final answer
    x = 30.63

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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.