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Finding the Fourth Proportional to 81.78, 112.64 and 74.36

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Solution

The fourth proportional to 81.78, 112.64 and 74.36 is: 102.42

Step by Step Solution

  1. Step 1: Write the proportion equation
    81.78 : 112.64 = 74.36 : x
  2. Step 2: Convert to fraction form
    81.78/112.64 = 74.36/x
  3. Step 3: Cross multiply
    81.78x = 112.64 × 74.36
  4. Step 4: Simplify right side
    81.78x = 8,375.91
  5. Step 5: Solve for x
    x = 8,375.91/81.78
  6. Step 6: Final answer
    x = 102.42

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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.