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Finding the Fourth Proportional to 81.20, 112.79 and 78.92

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Solution

The fourth proportional to 81.20, 112.79 and 78.92 is: 109.62

Step by Step Solution

  1. Step 1: Write the proportion equation
    81.20 : 112.79 = 78.92 : x
  2. Step 2: Convert to fraction form
    81.20/112.79 = 78.92/x
  3. Step 3: Cross multiply
    81.20x = 112.79 × 78.92
  4. Step 4: Simplify right side
    81.20x = 8,901.39
  5. Step 5: Solve for x
    x = 8,901.39/81.20
  6. Step 6: Final answer
    x = 109.62

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Why These Related Problems?

These problems maintain the same ratio (1.39) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.