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Finding the Fourth Proportional to 81.18, 111.20 and 78.48

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Solution

The fourth proportional to 81.18, 111.20 and 78.48 is: 107.50

Step by Step Solution

  1. Step 1: Write the proportion equation
    81.18 : 111.20 = 78.48 : x
  2. Step 2: Convert to fraction form
    81.18/111.20 = 78.48/x
  3. Step 3: Cross multiply
    81.18x = 111.20 × 78.48
  4. Step 4: Simplify right side
    81.18x = 8,726.58
  5. Step 5: Solve for x
    x = 8,726.58/81.18
  6. Step 6: Final answer
    x = 107.50

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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.