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Finding the Fourth Proportional to 81.96, 122.21 and 78.78

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Solution

The fourth proportional to 81.96, 122.21 and 78.78 is: 117.47

Step by Step Solution

  1. Step 1: Write the proportion equation
    81.96 : 122.21 = 78.78 : x
  2. Step 2: Convert to fraction form
    81.96/122.21 = 78.78/x
  3. Step 3: Cross multiply
    81.96x = 122.21 × 78.78
  4. Step 4: Simplify right side
    81.96x = 9,627.70
  5. Step 5: Solve for x
    x = 9,627.70/81.96
  6. Step 6: Final answer
    x = 117.47

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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.