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Finding the Fourth Proportional to 81.91, 112.89 and 57.31

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Solution

The fourth proportional to 81.91, 112.89 and 57.31 is: 78.98

Step by Step Solution

  1. Step 1: Write the proportion equation
    81.91 : 112.89 = 57.31 : x
  2. Step 2: Convert to fraction form
    81.91/112.89 = 57.31/x
  3. Step 3: Cross multiply
    81.91x = 112.89 × 57.31
  4. Step 4: Simplify right side
    81.91x = 6,469.66
  5. Step 5: Solve for x
    x = 6,469.66/81.91
  6. Step 6: Final answer
    x = 78.98

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Why These Related Problems?

These problems maintain the same ratio (1.38) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.