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Finding the Fourth Proportional to 81.78, 112.20 and 79.65

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Solution

The fourth proportional to 81.78, 112.20 and 79.65 is: 109.28

Step by Step Solution

  1. Step 1: Write the proportion equation
    81.78 : 112.20 = 79.65 : x
  2. Step 2: Convert to fraction form
    81.78/112.20 = 79.65/x
  3. Step 3: Cross multiply
    81.78x = 112.20 × 79.65
  4. Step 4: Simplify right side
    81.78x = 8,936.73
  5. Step 5: Solve for x
    x = 8,936.73/81.78
  6. Step 6: Final answer
    x = 109.28

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Why These Related Problems?

These problems maintain the same ratio (1.37) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.