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Finding the Fourth Proportional to 81.16, 120.77 and 78.61

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Solution

The fourth proportional to 81.16, 120.77 and 78.61 is: 116.98

Step by Step Solution

  1. Step 1: Write the proportion equation
    81.16 : 120.77 = 78.61 : x
  2. Step 2: Convert to fraction form
    81.16/120.77 = 78.61/x
  3. Step 3: Cross multiply
    81.16x = 120.77 × 78.61
  4. Step 4: Simplify right side
    81.16x = 9,493.73
  5. Step 5: Solve for x
    x = 9,493.73/81.16
  6. Step 6: Final answer
    x = 116.98

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Why These Related Problems?

These problems maintain the same ratio (1.49) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.