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Finding the Fourth Proportional to 81.91, 122.87 and 21.04

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Solution

The fourth proportional to 81.91, 122.87 and 21.04 is: 31.56

Step by Step Solution

  1. Step 1: Write the proportion equation
    81.91 : 122.87 = 21.04 : x
  2. Step 2: Convert to fraction form
    81.91/122.87 = 21.04/x
  3. Step 3: Cross multiply
    81.91x = 122.87 × 21.04
  4. Step 4: Simplify right side
    81.91x = 2,585.41
  5. Step 5: Solve for x
    x = 2,585.41/81.91
  6. Step 6: Final answer
    x = 31.56

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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.